There’s an odd article in the NY Times today on Marc Hauser’s hypothesis that the human mind contains a “moral grammar,” somewhat akin to a Chomskyan linguistic grammar. The article is odd because, while it acknowledges that Hauser’s idea is supported by almost no direct evidence, it never mentions any alternatives to Hauser’s theory. (If you’re going to write about a tentative hypothesis, you should at least mention that other hypotheses exist.) If you only read this article, you’d assume Hauser was the first person to argue that human morality is an evolved, biological trait, and that his moral grammar is the only biological approach to morality.
So what are some other alternatives? I think the most promising hypothesis is also the simplest: humans make moral decisions using the same cortical machinery that we use to make every decision. This means that you don’t need a specialized moral grammar to account for our odd moral instincts, since our moral instincts are directly derived from our more generalized decision-making instincts. Joshua Greene has done some of the pioneering work in the field. Greene argues that many of our moral decisions – just like all of our other decisions – result from the competition between our emotional limbic system (centered in the amygdala and dopaminergic midbrain) and a more “rational”, deliberate, and cognitive system that is located in the frontal cortex. Whenever we are confronted with a dilemma, these distinct systems compete for control. The area with the most activity–the feeling we feel most intensely–is the one that ultimately decides what we do.
According to this hypothesis, there is nothing unique about morality. It wasn’t handed down by God, and it isn’t derived from some unique mental grammar. From the perspective of our brain, moral decisions are nothing special. They are just another type of decision, subject to the same biases and instincts that distort all of our decisions. This is our original sin: that there is nothing special about sin. We decide whether or not kill somebody using the same brain regions that also decide whether or not buy a pack of gum, or eat an apple.