1. Nature Versus Nurture in the IQ Debate
Evidence suggests that family environmental factors may have an effect upon childhood IQ, accounting for up to a quarter of the variance. On the other hand, by late adolescence this correlation disappears, such that adoptive siblings are no more similar in IQ than strangers.[8] Moreover, adoption studies indicate that, by adulthood, adoptive siblings are no more similar in IQ than strangers (IQ correlation near zero), while full siblings show an IQ correlation of 0.6. Twin studies reinforce this pattern: monozygotic (identical) twins raised separately are highly similar in IQ (0.86), more so than dizygotic (fraternal) twins raised together (0.6) and much more than adoptive siblings (~0.0). [9] Consequently, in the context of the "nature versus nurture" debate, the "nature" component appears to be much more important than the "nurture" component in explaining IQ variance in the general adult population of the United States.
2. Nature versus Nurture in Personality Traits
Personality is a frequently cited example of a heritable trait that has been studied in twins and adoptions. Identical twins reared apart are far more similar in personality than randomly selected pairs of people. Likewise, identical twins are more similar than fraternal twins. Also, biological siblings are more similar in personality than adoptive siblings. Each observation suggests that personality is heritable to a certain extent. However, these same study designs allow for the examination of environment as well as genes. Adoption studies also directly measure the strength of shared family effects. Adopted siblings share only family environment. Unexpectedly, some adoption studies indicate that by adulthood the personalities of adopted siblings are no more similar than random pairs of strangers. This would mean that shared family effects on personality are zero by adulthood. As is the case with personality, non-shared environmental effects are often found to out-weigh shared environmental effects. That is, environmental effects that are typically thought to be life-shaping (such as family life) may have less of an impact than non-shared effects, which are harder to identify. One possible source of non-shared effects is the environment of pre-natal development. Random variations in the genetic program of development may be a substantial source of non-shared environment. These results suggest that "nurture" may not be the predominant factor in "environment".
3. Advanced techniques
The power of quantitative studies of heritable traits has been expanded by the development of new techniques. Developmental genetic analysis examines the effects of genes over the course of a human lifespan. For example, early studies of intelligence, which mostly examined young children, found heritability measures of 40 to 50 percent. Subsequent developmental genetic analyses have found that genetic contribution to intelligence increases over a lifespan,[10][11][12] reaching a heritability of 80 percent in adulthood.
Another advanced technique, multivariate genetic analysis, examines the genetic contribution to several traits that vary together. For example, multivariate genetic analysis has demonstrated that the genetic determinants of all specific cognitive abilities (e.g., memory, spatial reasoning, processing speed) overlap greatly, such that the genes associated with any specific cognitive ability will affect all others. Similarly, multivariate genetic analysis has found that genes that affect scholastic achievement completely overlap with the genes that affect cognitive ability.
Extremes analysis, examines the link between normal and pathological traits. For example, it is hypothesized that a given behavioral disorder may represent an extreme of a continuous distribution of a normal behavior and hence an extreme of a continuous distribution of genetic and environmental variation. Depression, phobias, and reading disabilities have been examined in this context.
For highly heritable traits, it is now possible to search for individual genes that contribute to variation in that trait. For example, several research groups have identified genetic loci that contribute to schizophrenia (Harrison and Owen, 2003).
4. Moral difficulties: eugenics, etc.
Some observers believe that modern science tends to give too much weight to the nature side of the argument, in part because of social consciousness. Historically, much of this debate has had undertones of racist and eugenicist policies — the notion of race as a scientific truth has often been assumed as a prerequisite in various incarnations of the nature versus nurture debate. In the past, heredity was often used as "scientific" justification for various forms of discrimination and oppression along racial and class lines. Works published in the United States since the 1960s that argue for the primacy of "nature" over "nurture" in determining certain characteristics, such as The Bell Curve, have been greeted with considerable controversy and scorn.
A critique of moral arguments against the nature side of the argument could be that they cross the is-ought gap. That is, they apply values to facts.
5. Philosophical difficulties: are the traits real?
It is sometimes a question whether the "trait" being measured is even a real thing. Much energy has been devoted to calculating the heritability of intelligence (usually the I.Q., or intelligence quotient), but there is still some disagreement as to what exactly "intelligence" is.
6. Philosophical difficulties: Biological determinism
If genes do contribute substantially to the development of personal characteristics such as intelligence and personality, then many wonder if this implies that genes determine who we are. Biological determinism is the thesis that genes determine who we are. Few if any scientists would make such a claim[citation needed]; however, many are accused of doing so. Defining the words "who" and "am" also present philosophical difficulties.
Others have pointed out that the premise of the "nature versus nurture" debate seems to negate the significance of free will[citation needed]. More specifically, if all our traits are determined by our genes, by our environment, by chance, or by some combination of these acting together, then there seems to be little room for free will. In any case, this line of reasoning suggests that the "nature versus nurture" debate tends to exaggerate the degree to which individual human behavior can be predicted based on knowledge of genetics and the environment. It should also be pointed out that biology may determine our abilities, but free will still determines what we do with our abilities.
7. Philosophical difficulties: is the problem real?
Many scientists feel that the very question opposing nature to nurture is a fallacy. Already in 1951, Calvin Hall in his seminal chapter[13] remarked that the discussion opposing nature and nurture was fruitless. If an environment is changed fundamentally, then the heritability of a character changes, too. Conversely, if the genetic composition of a population changes, then heritability will also change. As an example, we may use phenylketonuria (PKU), which causes brain damage and progressive mental retardation. PKU can be treated by the elimination of phenylalanine from the diet. Hence, a character (PKU) that used to have a virtually perfect heritability is not heritable any more if modern medicine is available. Similarly, within, say, an inbred strain of mice, no genetic variation is present and every character will have a zero heritability. If the complications of gene-environment interactions and correlations (see above) are added, then it appears to many that heritability, the epitome of the nature-nurture opposition, is "a station passed"[14]
8. Myths about identity
Within the debates surrounding cloning, for example, is the far-fetched contention that a Jesus or a Hitler could be "re-created" through genetic cloning. Current thinking finds this largely inaccurate, and discounts the possibility that the clone of anyone would grow up to be the same individual due to environmental variation. For example, like clones, identical twins are genetically identical, and unlike the hypothetical clones share the same family environment, yet they are not identical in personality and other traits.
Friday, August 24, 2007
HUMAN NATURE: Interaction of genes and environment
In only a very few cases is it fair to say that a trait is due almost entirely to nature, or almost entirely to nurture. [citation needed] In the case of most diseases now strictly identified as genetic, such as Huntington's disease, there is a better than 99.9% correlation between having the identified gene and the disease and a similar correlation for not having either. On the other hand, such traits as one's native language are entirely environmentally determined: linguists have found that any child (if capable of learning a language at all) can learn any human language with equal facility. With virtually all psychological traits however, there is an intermediate mix of nature and nurture, and opinions about the relative importance of each will often vary widely.
Examples of environmental, interactional, and genetic traits are:
Predominantly Environmental Interactional Predominantly Genetic
Specific Language Height Blood type
Specific Religion Weight Eye color
Skin color
The "two buckets" view of heritability.
The "two buckets" view of heritability.
More realistic "homogenous mudpie" view of heritability.
More realistic "homogenous mudpie" view of heritability.
Steven Pinker (2004) likewise described several examples:
concrete behavioral traits that patently depend on content provided by the home or culture—which language one speaks, which religion one practices, which political party one supports—are not heritable at all. But traits that reflect the underlying talents and temperaments—how proficient with language a person is, how religious, how liberal or conservative—are partially heritable.
When traits are determined by a complex interaction of genotype and environment it is possible to measure the heritability of a trait within a population. However, many non-scientists who encounter a report of a trait having a certain percentage heritability, imagine non-interactional, additive contributions of genes and environment to the trait. As an analogy, some laypeople may think of the degree of a trait being made up of two "buckets", genes and environment, each able to hold a certain capacity of the trait. But even for intermediate heritabilities, a trait is always shaped by both genetic dispositions and the environments in which people develop, merely with greater and lesser plasticities associated with these heritability measures.
Examples of environmental, interactional, and genetic traits are:
Predominantly Environmental Interactional Predominantly Genetic
Specific Language Height Blood type
Specific Religion Weight Eye color
Skin color
The "two buckets" view of heritability.
The "two buckets" view of heritability.
More realistic "homogenous mudpie" view of heritability.
More realistic "homogenous mudpie" view of heritability.
Steven Pinker (2004) likewise described several examples:
concrete behavioral traits that patently depend on content provided by the home or culture—which language one speaks, which religion one practices, which political party one supports—are not heritable at all. But traits that reflect the underlying talents and temperaments—how proficient with language a person is, how religious, how liberal or conservative—are partially heritable.
When traits are determined by a complex interaction of genotype and environment it is possible to measure the heritability of a trait within a population. However, many non-scientists who encounter a report of a trait having a certain percentage heritability, imagine non-interactional, additive contributions of genes and environment to the trait. As an analogy, some laypeople may think of the degree of a trait being made up of two "buckets", genes and environment, each able to hold a certain capacity of the trait. But even for intermediate heritabilities, a trait is always shaped by both genetic dispositions and the environments in which people develop, merely with greater and lesser plasticities associated with these heritability measures.
HUMAN NATURE : SOME APPROACHES
The Scientific Approach
In order to disentangle the effects of genes and environment, behavioral geneticists perform adoption and twin studies. Behavioral geneticists do not generally use the term "nurture" in order to explain that portion of the variance for a given trait (such as IQ or the Big Five personality traits) that can be attributed to environmental effects. Instead, two different types of environmental effects are distinguished: shared family factors (i.e., those shared by siblings, making them more similar) and nonshared factors (i.e., those that uniquely affect individuals, making siblings different). In order to express the portion of the variance that is due to the "nature" component, behavioral geneticists generally refer to the heritability of a trait.
With regard to the Big Five personality traits as well as adult IQ in the general U.S. population, the portion of the overall variance that can be attributed to shared family effects is often negligible. [4] On the other hand, most traits are thought to be at least partially heritable. In this context, the "nature" component of the variance is generally thought to be more important than that ascribed to the influence of family upbringing.
In her Pulitzer Prize-nominated book The Nurture Assumption, author Judith Harris argues that "nurture," as traditionally defined in terms family upbringing and socioeconomic status, does not effectively explain the variance for most traits (such as adult IQ and the Big Five personality traits) in the general population of the United States. On the contrary, Harris suggests that either peer groups or random environmental factors (i.e., those that are independent of family upbringing) are more important than family environmental effects [5] [6]
Although "nurture" has historically been referred to as the care given to children by the parents, with the mother playing a role of particular importance, this term is now regarded by some as any environmental (not genetic) factor in the contemporary nature versus nurture debate. Thus the definition of "nurture" has been expanded in order to include the influences on development arising from prenatal, parental, extended family and peer experiences, extending to influences such as media, marketing and socio-economic status. Indeed, a substantial source of environmental input to human nature may arise from stochastic variations in prenatal development. [citation needed]
Philosophical Approach
While classical theories regarding these matters were primarily concerned with the line between that which was voluntary (the ego, the self, and the personal will) and the involuntary (of Nature, Gods, etc.), this view was self-centric, which is to say deferential to authorities over the personal concepts; i.e. religious teaching and doctrine.
As science developed with new understandings of life's elemental nature (determined in its nature and behavior by the behaviors of constituent elements and prevailing physical phenomena, e.g. atoms, molecules, genes, force, and time), the categories that classical formalism defined came to be seen as arbitrary, and the trend of science since has been to develop away from the human-centered view to a more elemental, deterministic, reductionist view.
Scientific culture to this day functions within a social boundary imposed by the prevalence among laypeople of classical views. This boundary contains the impact of any scientific discoveries or observations on matters of human society. Thus nature versus nurture debates can be seen as attempts to fit new scientific ideas and developments into the classical formalist and self-based mold, since these debates arose from problems associated with reconciling the formalist notions of classical theories with emerging theories and new data. The gap between prevailing scientific opinion and prevailing lay opinion is reflected in popular science.
Advocates of a formalist view may discount completely the influence of one contributor or the other for the sake of some agenda, for example denying the influence of "nature" in order to preserve the idea of free will as the sole important determinant of behavior, a notion held to be of central importance in many religious, ethical, and legal systems, particularly in establishing culpability.
Heritability Estimates
This chart illustrates three patterns one might see when studying the influence of genes and environment on traits in individuals. Trait A shows a high sibling correlation, but little heritability (i.e. high shared environmental variance c2; low heritability h2). Trait B shows a high heritability since correlation of trait rises sharply with degree of genetic similarity. Trait C shows low heritibility, but also low correlations generally; this means Trait C has a high nonshared environmental variance e2. In other words, the degree to which individuals display Trait C has little to do with either genes or broadly predictable environmental factors—roughly, the outcome approaches random for an individual. Notice also that even identical twins raised in a common family rarely show 100% trait correlation.
This chart illustrates three patterns one might see when studying the influence of genes and environment on traits in individuals. Trait A shows a high sibling correlation, but little heritability (i.e. high shared environmental variance c2; low heritability h2). Trait B shows a high heritability since correlation of trait rises sharply with degree of genetic similarity. Trait C shows low heritibility, but also low correlations generally; this means Trait C has a high nonshared environmental variance e2. In other words, the degree to which individuals display Trait C has little to do with either genes or broadly predictable environmental factors—roughly, the outcome approaches random for an individual. Notice also that even identical twins raised in a common family rarely show 100% trait correlation.
Current thinking in biology discredits the notion that genes alone can determine a trait because genes are never sufficient in isolation. At the molecular level, DNA interacts in complex ways with signals from other genes and from the environment. At the level of individuals, particular genes influence the development of a trait in the context of a particular environment. Thus, measurements of the degree to which a trait is influenced by genes versus environment will depend on the particular environment and genes examined. In many cases, it has been found that genes may have a substantial contribution, including psychological traits such as intelligence and personality[7]. Yet, these traits may be largely influenced by environment in other circumstances, such as environmental deprivation.
A researcher seeking to quantify the influence of genes or environment on a trait needs to be able to separate the effects of one factor away from that of another. This kind of research often begins with attempts to calculate the heritability of a trait. Heritability quantifies the extent to which variation among individuals in a trait is due to variation in the genes those individuals carry. In animals where breeding and environments can be controlled experimentally, heritability can be determined relatively easily. Such experiments would be unethical for human research. This problem can be overcome by finding existing populations of humans that reflect the experimental setting the researcher wishes to create.
One way to determine the contribution of genes and environment to a trait is to study twins. In one kind of study, identical twins reared apart are compared to randomly selected pairs of people. The twins share identical genes, but different family environments. In another kind of twin study, identical twins reared together (who share family environment and genes) are compared to fraternal twins reared together (who also share family environment but only share half their genes). Another condition that permits the disassociation of genes and environment is adoption. In one kind of adoption study, biological siblings reared together (who share the same family environment and half their genes) are compared to adoptive siblings (who share their family environment but none of their genes).
Some have rightly pointed out that environmental inputs affect the expression of genes. This is one explanation of how environment can influence the extent to which a genetic disposition will actually manifest. The interactions of genes with environment, called gene-environment interaction, are another component of the nature-nurture debate. A classic example of gene-environment interaction is the ability of a diet low in the amino acid phenylalanine to partially suppress the genetic disease phenylketonuria. Yet another complication to the nature-nurture debate is the existence of gene-environment correlations. These correlations indicate that individuals with certain genotypes are more likely to find themselves in certain environments. Thus, it appears that genes can shape (the selection or creation of) environments. Even using experiments like those described above, it can be very difficult to determine convincingly the relative contribution of genes and environment.
In order to disentangle the effects of genes and environment, behavioral geneticists perform adoption and twin studies. Behavioral geneticists do not generally use the term "nurture" in order to explain that portion of the variance for a given trait (such as IQ or the Big Five personality traits) that can be attributed to environmental effects. Instead, two different types of environmental effects are distinguished: shared family factors (i.e., those shared by siblings, making them more similar) and nonshared factors (i.e., those that uniquely affect individuals, making siblings different). In order to express the portion of the variance that is due to the "nature" component, behavioral geneticists generally refer to the heritability of a trait.
With regard to the Big Five personality traits as well as adult IQ in the general U.S. population, the portion of the overall variance that can be attributed to shared family effects is often negligible. [4] On the other hand, most traits are thought to be at least partially heritable. In this context, the "nature" component of the variance is generally thought to be more important than that ascribed to the influence of family upbringing.
In her Pulitzer Prize-nominated book The Nurture Assumption, author Judith Harris argues that "nurture," as traditionally defined in terms family upbringing and socioeconomic status, does not effectively explain the variance for most traits (such as adult IQ and the Big Five personality traits) in the general population of the United States. On the contrary, Harris suggests that either peer groups or random environmental factors (i.e., those that are independent of family upbringing) are more important than family environmental effects [5] [6]
Although "nurture" has historically been referred to as the care given to children by the parents, with the mother playing a role of particular importance, this term is now regarded by some as any environmental (not genetic) factor in the contemporary nature versus nurture debate. Thus the definition of "nurture" has been expanded in order to include the influences on development arising from prenatal, parental, extended family and peer experiences, extending to influences such as media, marketing and socio-economic status. Indeed, a substantial source of environmental input to human nature may arise from stochastic variations in prenatal development. [citation needed]
Philosophical Approach
While classical theories regarding these matters were primarily concerned with the line between that which was voluntary (the ego, the self, and the personal will) and the involuntary (of Nature, Gods, etc.), this view was self-centric, which is to say deferential to authorities over the personal concepts; i.e. religious teaching and doctrine.
As science developed with new understandings of life's elemental nature (determined in its nature and behavior by the behaviors of constituent elements and prevailing physical phenomena, e.g. atoms, molecules, genes, force, and time), the categories that classical formalism defined came to be seen as arbitrary, and the trend of science since has been to develop away from the human-centered view to a more elemental, deterministic, reductionist view.
Scientific culture to this day functions within a social boundary imposed by the prevalence among laypeople of classical views. This boundary contains the impact of any scientific discoveries or observations on matters of human society. Thus nature versus nurture debates can be seen as attempts to fit new scientific ideas and developments into the classical formalist and self-based mold, since these debates arose from problems associated with reconciling the formalist notions of classical theories with emerging theories and new data. The gap between prevailing scientific opinion and prevailing lay opinion is reflected in popular science.
Advocates of a formalist view may discount completely the influence of one contributor or the other for the sake of some agenda, for example denying the influence of "nature" in order to preserve the idea of free will as the sole important determinant of behavior, a notion held to be of central importance in many religious, ethical, and legal systems, particularly in establishing culpability.
Heritability Estimates
This chart illustrates three patterns one might see when studying the influence of genes and environment on traits in individuals. Trait A shows a high sibling correlation, but little heritability (i.e. high shared environmental variance c2; low heritability h2). Trait B shows a high heritability since correlation of trait rises sharply with degree of genetic similarity. Trait C shows low heritibility, but also low correlations generally; this means Trait C has a high nonshared environmental variance e2. In other words, the degree to which individuals display Trait C has little to do with either genes or broadly predictable environmental factors—roughly, the outcome approaches random for an individual. Notice also that even identical twins raised in a common family rarely show 100% trait correlation.
This chart illustrates three patterns one might see when studying the influence of genes and environment on traits in individuals. Trait A shows a high sibling correlation, but little heritability (i.e. high shared environmental variance c2; low heritability h2). Trait B shows a high heritability since correlation of trait rises sharply with degree of genetic similarity. Trait C shows low heritibility, but also low correlations generally; this means Trait C has a high nonshared environmental variance e2. In other words, the degree to which individuals display Trait C has little to do with either genes or broadly predictable environmental factors—roughly, the outcome approaches random for an individual. Notice also that even identical twins raised in a common family rarely show 100% trait correlation.
Current thinking in biology discredits the notion that genes alone can determine a trait because genes are never sufficient in isolation. At the molecular level, DNA interacts in complex ways with signals from other genes and from the environment. At the level of individuals, particular genes influence the development of a trait in the context of a particular environment. Thus, measurements of the degree to which a trait is influenced by genes versus environment will depend on the particular environment and genes examined. In many cases, it has been found that genes may have a substantial contribution, including psychological traits such as intelligence and personality[7]. Yet, these traits may be largely influenced by environment in other circumstances, such as environmental deprivation.
A researcher seeking to quantify the influence of genes or environment on a trait needs to be able to separate the effects of one factor away from that of another. This kind of research often begins with attempts to calculate the heritability of a trait. Heritability quantifies the extent to which variation among individuals in a trait is due to variation in the genes those individuals carry. In animals where breeding and environments can be controlled experimentally, heritability can be determined relatively easily. Such experiments would be unethical for human research. This problem can be overcome by finding existing populations of humans that reflect the experimental setting the researcher wishes to create.
One way to determine the contribution of genes and environment to a trait is to study twins. In one kind of study, identical twins reared apart are compared to randomly selected pairs of people. The twins share identical genes, but different family environments. In another kind of twin study, identical twins reared together (who share family environment and genes) are compared to fraternal twins reared together (who also share family environment but only share half their genes). Another condition that permits the disassociation of genes and environment is adoption. In one kind of adoption study, biological siblings reared together (who share the same family environment and half their genes) are compared to adoptive siblings (who share their family environment but none of their genes).
Some have rightly pointed out that environmental inputs affect the expression of genes. This is one explanation of how environment can influence the extent to which a genetic disposition will actually manifest. The interactions of genes with environment, called gene-environment interaction, are another component of the nature-nurture debate. A classic example of gene-environment interaction is the ability of a diet low in the amino acid phenylalanine to partially suppress the genetic disease phenylketonuria. Yet another complication to the nature-nurture debate is the existence of gene-environment correlations. These correlations indicate that individuals with certain genotypes are more likely to find themselves in certain environments. Thus, it appears that genes can shape (the selection or creation of) environments. Even using experiments like those described above, it can be very difficult to determine convincingly the relative contribution of genes and environment.
HUMAN NATURE : TABULA RASA - JOHN LOCKE
In Eastern philosophy, the notion of tabula rasa is not explicitly mentioned, though there are many reasons to consider that it is a much relied upon idea.[citation needed]
In Western philosophy, traces of the idea that came to be called the tabula rasa appear as early as the writings of Aristotle:
What the mind thinks must be in it in the same sense as letters are on a tablet (grammateion) which bears no actual writing (grammenon); this is just what happens in the case of the mind. (Aristotle, On the Soul, 3.4.430a1).
Aristotle writes of the unscribed tablet in what is probably the first textbook of psychology in the Western canon, his treatise Περι Ψυχης (De Anima or On the Soul). However, besides some arguments by the Stoics and Peripatetics, the Aristotelian notion of the mind as a blank slate went much unnoticed for nearly 1800 years.
But the human intellect, which is the lowest in the order of intellects and the most removed from the perfection of the Divine intellect, is in potency with regard to things intelligible, and is at first "like a clean tablet on which nothing is written", as the Philosopher [Aristotle] says. (Aquinas, Summa Theologica 1.79.2).
In the 13th century, St. Thomas Aquinas brought the Aristotelian notion back to the forefront of modern thought. This notion sharply contrasted with the previously held Platonic notions of the human mind as an entity that pre-existed somewhere in the heavens, before being sent down to join a body here on Earth (see Plato's Phaedo and Apology, as well as others). St. Bonaventure (also 13th century) was one of Aquinas' fiercest intellectual opponents, offering some of the strongest arguments towards the Platonic idea of the mind.
Aquinas's writings on the tabula rasa theory stood untested and unprogressed for several centuries. In fact, our modern idea of the theory is mostly attributed to John Locke's expression of the idea in the 17th century. In Locke's philosophy, tabula rasa was the theory that the (human) mind is at birth a "blank slate" without rules for processing data, and that data is added and rules for processing are formed solely by one's sensory experiences. The notion is central to Lockean empiricism. As understood by Locke, tabula rasa meant that the mind of the individual was born "blank", and it also emphasized the individual's freedom to author his or her own soul. Each individual was free to define the content of his or her character - but his or her basic identity as a member of the human species cannot be so altered. It is from this presumption of a free, self-authored mind combined with an immutable human nature that the Lockean doctrine of "natural" rights derives.
Tabula Rasa is also featured in Sigmund Freud's psychoanalysis. Freud depicted personality traits as being formed by family dynamics (see Oedipus complex, etc.). Freud's theories show that one can downplay genetic and congenital influences on human personality without advocating free will. In psychosanalysis, one is largely determined by one's upbringing.
The tabula rasa concept became popular in social sciences in the 20th century. Eugenics (mainstream in the late 19th and early 20th centuries) came to be seen not as a sound policy but as a crime. The idea that genes (or simply "blood") determined character took on racist overtones. By the 70s, scientists had come to see gender identity as socially constructed rather than rooted in genetics (see John Money), a concept still current (see Anne Fausto-Sterling). This swing of the pendulum accompanied suspicion of innate differences in general (see racism) and a propensity to "manage" society, where the real power must be if people are born blank.
In the last few decades, twin studies, studies of adopted children, and the David Reimer case have demonstrated genetic influence on (if not strict determination of) personal characteristics, such as IQ, alcoholism, gender identity, and other traits.[3]
In Western philosophy, traces of the idea that came to be called the tabula rasa appear as early as the writings of Aristotle:
What the mind thinks must be in it in the same sense as letters are on a tablet (grammateion) which bears no actual writing (grammenon); this is just what happens in the case of the mind. (Aristotle, On the Soul, 3.4.430a1).
Aristotle writes of the unscribed tablet in what is probably the first textbook of psychology in the Western canon, his treatise Περι Ψυχης (De Anima or On the Soul). However, besides some arguments by the Stoics and Peripatetics, the Aristotelian notion of the mind as a blank slate went much unnoticed for nearly 1800 years.
But the human intellect, which is the lowest in the order of intellects and the most removed from the perfection of the Divine intellect, is in potency with regard to things intelligible, and is at first "like a clean tablet on which nothing is written", as the Philosopher [Aristotle] says. (Aquinas, Summa Theologica 1.79.2).
In the 13th century, St. Thomas Aquinas brought the Aristotelian notion back to the forefront of modern thought. This notion sharply contrasted with the previously held Platonic notions of the human mind as an entity that pre-existed somewhere in the heavens, before being sent down to join a body here on Earth (see Plato's Phaedo and Apology, as well as others). St. Bonaventure (also 13th century) was one of Aquinas' fiercest intellectual opponents, offering some of the strongest arguments towards the Platonic idea of the mind.
Aquinas's writings on the tabula rasa theory stood untested and unprogressed for several centuries. In fact, our modern idea of the theory is mostly attributed to John Locke's expression of the idea in the 17th century. In Locke's philosophy, tabula rasa was the theory that the (human) mind is at birth a "blank slate" without rules for processing data, and that data is added and rules for processing are formed solely by one's sensory experiences. The notion is central to Lockean empiricism. As understood by Locke, tabula rasa meant that the mind of the individual was born "blank", and it also emphasized the individual's freedom to author his or her own soul. Each individual was free to define the content of his or her character - but his or her basic identity as a member of the human species cannot be so altered. It is from this presumption of a free, self-authored mind combined with an immutable human nature that the Lockean doctrine of "natural" rights derives.
Tabula Rasa is also featured in Sigmund Freud's psychoanalysis. Freud depicted personality traits as being formed by family dynamics (see Oedipus complex, etc.). Freud's theories show that one can downplay genetic and congenital influences on human personality without advocating free will. In psychosanalysis, one is largely determined by one's upbringing.
The tabula rasa concept became popular in social sciences in the 20th century. Eugenics (mainstream in the late 19th and early 20th centuries) came to be seen not as a sound policy but as a crime. The idea that genes (or simply "blood") determined character took on racist overtones. By the 70s, scientists had come to see gender identity as socially constructed rather than rooted in genetics (see John Money), a concept still current (see Anne Fausto-Sterling). This swing of the pendulum accompanied suspicion of innate differences in general (see racism) and a propensity to "manage" society, where the real power must be if people are born blank.
In the last few decades, twin studies, studies of adopted children, and the David Reimer case have demonstrated genetic influence on (if not strict determination of) personal characteristics, such as IQ, alcoholism, gender identity, and other traits.[3]
HUMAN NATURE: MORALITY & PURPOSE
There are a number of views regarding the origin and nature of human morality
* Moral realism or moral objectivism holds that moral codes exist outside of human opinion -- that certain things are right or wrong regardless of human opinion on the topic. Objective morality may be seen as stemming from the inherent nature of humanity, divine command, or both.
* Moral relativism holds that moral codes are a function of human values and social structures, and hold no meaning outside social convention.
* Moral absolutism is the view that certain acts are right or wrong regardless of context.
* Moral universalism compromises between moral relativism and moral absolutism and holds that there is, or should be, a common universal core of morality.
* Materialism and philosophical naturalism hold that there is no external purpose to human life. Proponents of this view often adopt the philosophy of secular humanism.
* Teleology holds that there is inherent purpose to human existence. This purpose may arise from the inherent nature of humanity itself (what a human is "supposed to be," as in the case of objectivist philosophy), from mankind's relationship to the divine (what God wants humanity to be, as in the case of religion), or from both (as when the divine commands are seen as being in accord with the inherent nature of humanity and humanity's best interests).
* Moral realism or moral objectivism holds that moral codes exist outside of human opinion -- that certain things are right or wrong regardless of human opinion on the topic. Objective morality may be seen as stemming from the inherent nature of humanity, divine command, or both.
* Moral relativism holds that moral codes are a function of human values and social structures, and hold no meaning outside social convention.
* Moral absolutism is the view that certain acts are right or wrong regardless of context.
* Moral universalism compromises between moral relativism and moral absolutism and holds that there is, or should be, a common universal core of morality.
* Materialism and philosophical naturalism hold that there is no external purpose to human life. Proponents of this view often adopt the philosophy of secular humanism.
* Teleology holds that there is inherent purpose to human existence. This purpose may arise from the inherent nature of humanity itself (what a human is "supposed to be," as in the case of objectivist philosophy), from mankind's relationship to the divine (what God wants humanity to be, as in the case of religion), or from both (as when the divine commands are seen as being in accord with the inherent nature of humanity and humanity's best interests).
HUMAN NATURE: STATE of NATURE
State of nature refers to philosophical assertions regarding the condition of humans before social factors are imposed, thus attempting to describe the "natural essence" of human nature.
* Views which see humans as inherently good:
o According to John Locke, humans in the state of nature have perfect freedom to order their actions according to the laws of nature, without having to ask permission to act from any other person. People are of equal value, and treat each other as they would want to be treated. People only leave the state of nature when they consent to take part in a community in order to protect their property rights. [1]
o According to Rousseau, humans in the state of nature are naturally good, and bad habits are the product of corrupting civilization;
* Views which see humans as morally neutral:
o According to Pelagius, humans in the state of nature are not tainted by original sin, but are instead fully capable of choosing good or evil.
o According to social determinism and biological determinism, human behavior is determined by biological and social factors, so inherent human instincts are never truly to blame for actions generally considered "bad" nor truly credited with actions generally considered "good."
* Views which see humans as inherently bad:
o According to Hobbes, humans in the state of nature are inherently in a "war of all against all," and life in that state is ultimately "nasty, brutish, and short." To Hobbes, this state of nature is remedied by good government.
o According to the Christian doctrine of original sin, human beings are inherently corrupt creatures stained by the sin of Adam, and can only be redeemed by the grace of God through faith in the righteousness of Jesus Christ, whom they believe to be His morally perfect Son. In Protestant theology, the virgin birth is believed to make this possible, as original sin is thought to pass from the seed of man. Catholicism, however, holds that the natures of both Jesus and His mother Mary, as a holy vessel for the Messiah, were uncorrupted by original sin.
o According to Bertrand Russell moral evil or sin is derived from the instincts that have been transmitted to us from our ancestry of beasts of prey. This ancestry originated when certain animals became omnivorous and employed predation (killing and thievery) in order periodically to ingurgitate the flesh as well as the fruit and produce of other once-living things to support metabolism in competition with other animals for scarce food-animal and food-plant sources in the predatory environment in which we evolved. Thus, the simple fact that we humans must eat other life or else starve, die and rot is the probable primordial origin of contemporary and historical moral evil; i.e., the bad things we do to each other by lying, cheating, slandering, thieving and slaughtering.
* Views which see humans as inherently good:
o According to John Locke, humans in the state of nature have perfect freedom to order their actions according to the laws of nature, without having to ask permission to act from any other person. People are of equal value, and treat each other as they would want to be treated. People only leave the state of nature when they consent to take part in a community in order to protect their property rights. [1]
o According to Rousseau, humans in the state of nature are naturally good, and bad habits are the product of corrupting civilization;
* Views which see humans as morally neutral:
o According to Pelagius, humans in the state of nature are not tainted by original sin, but are instead fully capable of choosing good or evil.
o According to social determinism and biological determinism, human behavior is determined by biological and social factors, so inherent human instincts are never truly to blame for actions generally considered "bad" nor truly credited with actions generally considered "good."
* Views which see humans as inherently bad:
o According to Hobbes, humans in the state of nature are inherently in a "war of all against all," and life in that state is ultimately "nasty, brutish, and short." To Hobbes, this state of nature is remedied by good government.
o According to the Christian doctrine of original sin, human beings are inherently corrupt creatures stained by the sin of Adam, and can only be redeemed by the grace of God through faith in the righteousness of Jesus Christ, whom they believe to be His morally perfect Son. In Protestant theology, the virgin birth is believed to make this possible, as original sin is thought to pass from the seed of man. Catholicism, however, holds that the natures of both Jesus and His mother Mary, as a holy vessel for the Messiah, were uncorrupted by original sin.
o According to Bertrand Russell moral evil or sin is derived from the instincts that have been transmitted to us from our ancestry of beasts of prey. This ancestry originated when certain animals became omnivorous and employed predation (killing and thievery) in order periodically to ingurgitate the flesh as well as the fruit and produce of other once-living things to support metabolism in competition with other animals for scarce food-animal and food-plant sources in the predatory environment in which we evolved. Thus, the simple fact that we humans must eat other life or else starve, die and rot is the probable primordial origin of contemporary and historical moral evil; i.e., the bad things we do to each other by lying, cheating, slandering, thieving and slaughtering.
SPIRITUAL VS NATURE
Another often-discussed aspect of human nature is the existence and relationship of the physical body with a spirit or soul that transcends the human's physical attributes, as well as the existence of any transcendent purpose. In this area, there are three dominant views:
* The philosophical naturalist position is that humans are entirely natural, with no spiritual component or transcendent purpose. Subsets of the naturalist view include the materialist and physicalist positions, which hold that humans are entirely physical. However, some naturalists are also dualists about mind and body. Naturalism, combined with the natural and social sciences, views humans as the unplanned product of evolution, which operated in part by natural selection on random mutations. Philosophical naturalists do not believe in a supernatural afterlife. While philosophical naturalism is often assailed as an unacceptable view of human nature, it is promoted by many prominent philosophers and thinkers. The philosophical naturalist often will view religious belief as similar to superstition and as the product of unsound or magical thinking.
* In contrast to materialism, there is the Platonic or idealist position. It can be expressed in many ways, but in essence it is the view that there is a distinction between appearance and reality, and that the world we see around us is simply a reflection of some higher, divine existence, of which the human (and perhaps also the animal) soul/mind or spirit may be part. In his Republic, Book VII, Plato represents humankind as prisoners chained from birth inside an underground cave, unable to move their heads, and therefore able to see only the shadows on the walls created by a fire outside the cave, shadows that, in their ignorance, the cave dwellers mistake for reality. For Plato, therefore, the soul is a spirit that uses the body. It is in a non-natural state of union, and longs to be freed from its bodily prison (cf. Republic, X, 611).
* Between materialism and idealism lies the thought of St. Thomas Aquinas, whose system of thought is known as Thomism. His thought is, in essence, a synthesis of Christian theology and the philosophy of Aristotle. Aristotle describes man as a "rational animal," i.e., a single, undivided being that is at once animal (material) and rational (intellectual soul). Drawing from Aristotelian hylomorphism, The soul is seen as the substantial form of the body (matter). The soul, as the substantial form, is what is universal, or common, to all humanity, and therefore, is indicative of human nature; that which differentiates one person from another is matter, which Aquinas refers to as the principle of individuation. The human soul is characterized as spiritual, immortal, substantial, and subsistent: it is the spiritual and vital principle of the human being, but is also dependent on the body in a variety of ways in order to possess these characteristics. Thus, no division is made between the "physical" and the "spiritual," though they are in fact distinct. This position differentiates Thomism from both materialism and idealism. Unlike idealism, it holds that the visible universe is not a mere shadow of a transcendent reality, but instead is fully real in and of itself. However, unlike materialism, Thomism holds that empiricism and philosophy, when properly exercised, lead inevitably to reasonable belief in God, the human soul, and moral objectivism. Thus, to a Thomist, it is obvious from the evidence that there is a God and an eternal soul.
* The philosophical naturalist position is that humans are entirely natural, with no spiritual component or transcendent purpose. Subsets of the naturalist view include the materialist and physicalist positions, which hold that humans are entirely physical. However, some naturalists are also dualists about mind and body. Naturalism, combined with the natural and social sciences, views humans as the unplanned product of evolution, which operated in part by natural selection on random mutations. Philosophical naturalists do not believe in a supernatural afterlife. While philosophical naturalism is often assailed as an unacceptable view of human nature, it is promoted by many prominent philosophers and thinkers. The philosophical naturalist often will view religious belief as similar to superstition and as the product of unsound or magical thinking.
* In contrast to materialism, there is the Platonic or idealist position. It can be expressed in many ways, but in essence it is the view that there is a distinction between appearance and reality, and that the world we see around us is simply a reflection of some higher, divine existence, of which the human (and perhaps also the animal) soul/mind or spirit may be part. In his Republic, Book VII, Plato represents humankind as prisoners chained from birth inside an underground cave, unable to move their heads, and therefore able to see only the shadows on the walls created by a fire outside the cave, shadows that, in their ignorance, the cave dwellers mistake for reality. For Plato, therefore, the soul is a spirit that uses the body. It is in a non-natural state of union, and longs to be freed from its bodily prison (cf. Republic, X, 611).
* Between materialism and idealism lies the thought of St. Thomas Aquinas, whose system of thought is known as Thomism. His thought is, in essence, a synthesis of Christian theology and the philosophy of Aristotle. Aristotle describes man as a "rational animal," i.e., a single, undivided being that is at once animal (material) and rational (intellectual soul). Drawing from Aristotelian hylomorphism, The soul is seen as the substantial form of the body (matter). The soul, as the substantial form, is what is universal, or common, to all humanity, and therefore, is indicative of human nature; that which differentiates one person from another is matter, which Aquinas refers to as the principle of individuation. The human soul is characterized as spiritual, immortal, substantial, and subsistent: it is the spiritual and vital principle of the human being, but is also dependent on the body in a variety of ways in order to possess these characteristics. Thus, no division is made between the "physical" and the "spiritual," though they are in fact distinct. This position differentiates Thomism from both materialism and idealism. Unlike idealism, it holds that the visible universe is not a mere shadow of a transcendent reality, but instead is fully real in and of itself. However, unlike materialism, Thomism holds that empiricism and philosophy, when properly exercised, lead inevitably to reasonable belief in God, the human soul, and moral objectivism. Thus, to a Thomist, it is obvious from the evidence that there is a God and an eternal soul.
HUMAN NATURE
HUMAN NATURE:Brief history
In pre-modern and non-scientific understandings of nature, human nature is understood with reference to final and formal causes. Such understandings imply the existence of a divine interest in human nature, and/or the existence of an ideal, "idea," or "form" of a human which exists independently of individual humans.
According to the accepted modern scientific understanding, human nature is the range of human behavior that is believed to be normal and/or invariant over long periods of time and across very different cultural contexts.
The existence of an invariable human nature is a subject of much historical debate, particularly in modern times. Most famously, Darwin gave a widely accepted scientific argument that humans and other animal species have no truly fixed nature. Before him, the malleability of man had been asserted by Jean Jacques Rousseau.
Since the mid-19th century, the concept of human nature has been called into question by thinkers such as Hegel, Marx, Nietzsche, Sartre, a number of structuralists and postmodernists. The concept has also been challenged by views such as behaviorism, determinism, and the chemical model within modern psychiatry and psychology, which have tended to emphasize the idea that human beings might conceivably be explained as "matter in motion" in a way that is similar to the rest of nature. Recently the biologist E. O. Wilson formulated a scientific definition.
[edit] Metaphysics and ethics
There are a number of perspectives regarding the fundamental nature and substance of humans. These are by no means mutually exclusive, and the following list is by no means exhaustive:
* Philosophical naturalism (which includes materialism and rationalism) encompasses a set of views that humans are purely natural phenomena; sophisticated beings that evolved to our present state through natural mechanisms such as evolution. Humanist philosophers determine good and evil by appeal to universal human qualities, but other naturalists regard these terms as mere labels placed on how well individual behaviour conforms to societal expectations, and is the result of our psychology and socialization.
* Abrahamic religion holds that a human is a spiritual being which was deliberately created (ex nihilo) by a single God in his image, and exists in continued relationship with God. Good and evil are defined in terms of how well human beings conform to God's character or God's law.
* Polytheistic or animistic notions vary, but generally regard human beings as citizens in a world populated by other intelligent spiritual or mythological beings, such as gods, demons, ghosts, etc. In these cases, human evil is often regarded as the result of supernatural influences or mischief (although may have many other causes as well).
* Holistic, pantheistic, and panentheistic spiritual traditions regard humanity as existing within God or as a part of Divine cosmos. In this case, human "evil" is usually regarded as the result of ignorance of this universal Divine nature. Traditions of this kind include Dharmic religions and other forms of Eastern philosophy (including Buddhism and Taoism), and Western philosophy such as Stoicism, Neoplatonism, or Spinoza's pantheistic cosmology. Certain kinds of polytheism, animism, and monism have similar interpretations.
[edit] Free will and determinism
The issue of free will and determinism underlies much of the debate about human nature. Free will, or agency, refers to the ability of humans to make genuinely free choices (in some sense). As it relates to humans, the thesis of determinism implies that human choices are fully caused by internal and external forces.
* Incompatibilism holds that determinism and free will are contradictory (i.e. both cannot be true). Incompatibilist views can either deny or accept will.
o Incompatibilist views holding to free will include:
+ Libertarianism holds that the human perception of free choice in action is genuine, rather than seemingly genuine, so that some of our actions are performed without there being any compulsion by internal or external forces to do so (i.e., indeterminism).
+ Thomism holds that humans have a genuine experience of free will, and this experience of free will is evidence of a soul that transcends the mere physical components of the human being.
o Incompatibilist views that deny free will include:
+ Determinism refers to the logic that humans, like all physical phenomena, are subject to cause and effect. Determinism also holds that our actions stem from environmental, biological, or theological factors. A common misconception is that all determinists are fatalists, who believe that deliberation is pointless as the future is already caused; when in fact most determinists hold the idea that we should deliberate on our actions and that deliberating on our actions is part of the complex interplay between cause and effect.
+ Predestination is the position that God orchestrates all the events in the universe, human and otherwise, according to his will; however he does it in a way that includes the free choices of humans.
+ Biological determinism and social determinism are the views that human actions are determined by their biology and social interaction, respectively. The debate between these two positions is known as nature versus nurture.
* Compatibilism is the view that free will and determinism coexist. Compatibilist views include:
o Human compatibilitism is the view that they are compatible because free will is merely the hypothetical ability to choose differently if one were differently disposed according to the physical factors of determinism.
o Molinism is the view that God is able to predestine all events on Earth because he knows in advance what people will freely choose.
o Contemporary compatibilists seek definitions of free will that permit determinism.
In pre-modern and non-scientific understandings of nature, human nature is understood with reference to final and formal causes. Such understandings imply the existence of a divine interest in human nature, and/or the existence of an ideal, "idea," or "form" of a human which exists independently of individual humans.
According to the accepted modern scientific understanding, human nature is the range of human behavior that is believed to be normal and/or invariant over long periods of time and across very different cultural contexts.
The existence of an invariable human nature is a subject of much historical debate, particularly in modern times. Most famously, Darwin gave a widely accepted scientific argument that humans and other animal species have no truly fixed nature. Before him, the malleability of man had been asserted by Jean Jacques Rousseau.
Since the mid-19th century, the concept of human nature has been called into question by thinkers such as Hegel, Marx, Nietzsche, Sartre, a number of structuralists and postmodernists. The concept has also been challenged by views such as behaviorism, determinism, and the chemical model within modern psychiatry and psychology, which have tended to emphasize the idea that human beings might conceivably be explained as "matter in motion" in a way that is similar to the rest of nature. Recently the biologist E. O. Wilson formulated a scientific definition.
[edit] Metaphysics and ethics
There are a number of perspectives regarding the fundamental nature and substance of humans. These are by no means mutually exclusive, and the following list is by no means exhaustive:
* Philosophical naturalism (which includes materialism and rationalism) encompasses a set of views that humans are purely natural phenomena; sophisticated beings that evolved to our present state through natural mechanisms such as evolution. Humanist philosophers determine good and evil by appeal to universal human qualities, but other naturalists regard these terms as mere labels placed on how well individual behaviour conforms to societal expectations, and is the result of our psychology and socialization.
* Abrahamic religion holds that a human is a spiritual being which was deliberately created (ex nihilo) by a single God in his image, and exists in continued relationship with God. Good and evil are defined in terms of how well human beings conform to God's character or God's law.
* Polytheistic or animistic notions vary, but generally regard human beings as citizens in a world populated by other intelligent spiritual or mythological beings, such as gods, demons, ghosts, etc. In these cases, human evil is often regarded as the result of supernatural influences or mischief (although may have many other causes as well).
* Holistic, pantheistic, and panentheistic spiritual traditions regard humanity as existing within God or as a part of Divine cosmos. In this case, human "evil" is usually regarded as the result of ignorance of this universal Divine nature. Traditions of this kind include Dharmic religions and other forms of Eastern philosophy (including Buddhism and Taoism), and Western philosophy such as Stoicism, Neoplatonism, or Spinoza's pantheistic cosmology. Certain kinds of polytheism, animism, and monism have similar interpretations.
[edit] Free will and determinism
The issue of free will and determinism underlies much of the debate about human nature. Free will, or agency, refers to the ability of humans to make genuinely free choices (in some sense). As it relates to humans, the thesis of determinism implies that human choices are fully caused by internal and external forces.
* Incompatibilism holds that determinism and free will are contradictory (i.e. both cannot be true). Incompatibilist views can either deny or accept will.
o Incompatibilist views holding to free will include:
+ Libertarianism holds that the human perception of free choice in action is genuine, rather than seemingly genuine, so that some of our actions are performed without there being any compulsion by internal or external forces to do so (i.e., indeterminism).
+ Thomism holds that humans have a genuine experience of free will, and this experience of free will is evidence of a soul that transcends the mere physical components of the human being.
o Incompatibilist views that deny free will include:
+ Determinism refers to the logic that humans, like all physical phenomena, are subject to cause and effect. Determinism also holds that our actions stem from environmental, biological, or theological factors. A common misconception is that all determinists are fatalists, who believe that deliberation is pointless as the future is already caused; when in fact most determinists hold the idea that we should deliberate on our actions and that deliberating on our actions is part of the complex interplay between cause and effect.
+ Predestination is the position that God orchestrates all the events in the universe, human and otherwise, according to his will; however he does it in a way that includes the free choices of humans.
+ Biological determinism and social determinism are the views that human actions are determined by their biology and social interaction, respectively. The debate between these two positions is known as nature versus nurture.
* Compatibilism is the view that free will and determinism coexist. Compatibilist views include:
o Human compatibilitism is the view that they are compatible because free will is merely the hypothetical ability to choose differently if one were differently disposed according to the physical factors of determinism.
o Molinism is the view that God is able to predestine all events on Earth because he knows in advance what people will freely choose.
o Contemporary compatibilists seek definitions of free will that permit determinism.
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