There has been a flurry of attention recently to the notion of a “poverty of the stimulus” argument in moral development. Briefly, the “Argument from the Poverty of the Stimulus” (”APoS”) was advanced by Noam Chomsky in support of his theory regarding an innate (”nativist”), universal human grammar, on which children draw as they learn language. (The argument has a formal structure, but it basically consists in the observation that the specific grammar of the particular language the child is exposed to is underdetermined by the stimulus the child receives - the sentences the child hears from others. Given a limited set of inputs, a variety of possible grammatical structures capable of producing those sentences could be deduced, so the child cannot learn one particular language from that input; instead, the child learns the one language that is capable of generating the set of sentences it has heard and which is possible under the set of universal grammatical rules hardwired into its brain. When it has heard enough sentences, only one plausible grammatical structure will be available from within the universal grammar the child possesses, although many possible grammars could still have been deduced if that constraint were not present. The existence of the universal grammar is required to make accurate language acquisition possible in spite of the poverty of the stimulus, and therefore the fact that language is acquired at all is evidence for such a universal grammar and therefore the truth of the nativist theory of language.) The moral parallel is the idea that there is a universal, nativist moral sense. Just as the existence of hardwired language rules allows the child to generate new sentences, despite its exposure to impoverished language stimuli previously, so the nativist moral sense allows the child to make moral judgments regarding situations it has not already encountered. Just as the nativist language theory is a refutation of the empiricist school of language - holding that language skills are acquired essentially by behaviorist-style mimicry - the nativist moral theory is a refutation of the claim that moral judgments are culturally determined.

Adam Colber of Neuroethics & Law Blog has a good post, referencing an interesting recent journal article on the topic. Kyle Swan of Pea Soup had a more detailed discussion of the subject about 18 months ago (I just found the link after being “stimulated” by Colber’s post), which provides some excellent speculation and a very insightful comments thread. He also provides a useful bibliography, and links to a preceding series of posts on moral realism. There’s some excellent work going on over there at Pea Soup.

But what does this all cash out to?

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