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Psychologist and Biologist, Harvard University: Author, Moral Minds
A universal grammar of [mental] life

The recent explosion of work in molecular evolution and developmental biology has, for the first time, made it possible to propose a radical new theory of mental life that if true, will forever rewrite the textbooks and our way of thinking about our past and future. It explains both the universality of our thoughts as well as the unique signatures that demarcate each human culture, past, present and future.

The theory I propose is that human mental life is based on a few simple, abstract, yet expressively powerful rules or computations together with an instructive learning mechanism that prunes the range of possible systems of language, music, mathematics, art, and morality to a limited set of culturally expressed variants. In many ways, this view isn't new or radical. It stems from thinking about the seemingly constrained ways in which relatively open ended or generative systems of expression create both universal structure and limited variation.

Unfortunately, what appears to be a rather modest proposal on some counts, is dangerous on another. It is dangerous to those who abhor biologically grounded theories on the often misinterpreted perspective that biology determines our fate, derails free will, and erases the soul. But a look at systems other than the human mind makes it transparently clear that the argument from biological endowment does not entail any of these false inferences.

For example, we now understand that our immune systems don't learn from the environment how to tune up to the relevant problems. Rather, we are equipped with a full repertoire of antibodies to deal with a virtually limitless variety of problems, including some that have not yet even emerged in the history of life on earth. This initially seems counter-intuitive: how could the immune system have evolved to predict the kinds of problems we might face? The answer is that it couldn't.

What it evolved instead was a set of molecular computations that, in combination with each other, can handle an infinitely larger set of conditions than any single combination on its own. The role of the environment is as instructor, functionally telling the immune system about the current conditions, resulting in a process of pairing down of initial starting options.

The pattern of change observed in the immune system, characterized by an initial set of universal computations or options followed by an instructive process of pruning, is seen in systems as disparate as the genetic mechanisms underlying segmented body parts in vertebrates, the basic body plan of land plants involving the shoot system of stem and leaves, and song development in birds. Songbirds are particularly interesting as the system for generating a song seems to be analogous in important ways to our capacity to generate a specific language. Humans and songbirds start with a species-specific capacity to build language and song respectively, and this capacity has limitless expressive power. Upon delivery and hatching, and possibly a bit before, the local acoustic environment begins the process of instruction, pruning the possible languages and songs down to one or possibly two. The common thread here is a starting state of universal computations or options followed by an instructive process of pruning, ending up with distinctive systems that share an underlying common core. Hard to see how anyone could find this proposal dangerous or off-putting, or even wrong!

Now jump laterally, and make the move to aesthetics and ethics. Our minds are endowed with universal computations for creating and judging art, music, and morally relevant actions. Depending upon where we are born, we will find atonal music pleasing or disgusting, and infanticide obligatory or abhorrent. The common or universal core is, for music, a set of rules for combining together notes to alter our emotions, and for morality, a different set of rules for combining the causes and consequences of action to alter our permissibility judgments.

To say that we are endowed with a universal moral sense is not to say that we will do the right or wrong thing, with any consistency. The idea that there is a moral faculty, grounded in our biology, says nothing at all about the good, the bad or the ugly. What it says is that we have evolved particular biases, designed as a function of selection for particular kinds of fit to the environment, under particular constraints. But nothing about this claim leads to the good or the right or the permissible.

The reason this has to be the case is twofold: there is not only cultural variation but environmental variation over evolutionary time. What is good for us today may not be good for us tomorrow. But the key insight delivered by the nativist perspective is that we must understand the nature of our biases in order to work toward some good or better world, realizing all along that we are constrained. Appreciating the choreography between universal options and instructive pruning is only dangerous if misused to argue that our evolved nature is good, and what is good is right. That's bad.