Metaphors are brilliant, even in science. Descartes likened the world to a machine, Newton to a clock, Darwin used breeding as an analogy for evolution; and lately the mind to a computer. Noam Chomsky had an idea that the brain is "hardwired" to acquire language, an "innate" language capacity, a universal grammar so to speak. This explains why we learn it so easily, but yet we have particular differences (English, Chinese, Spanish). Hauser, in this book, takes it from Chomsky and applies it to morality. He argues that we have a "univesal moral grammer," an innate set of moral principles. This explains why almost all humans agree on the "big issues" (you shouldn't kill people), but show a wonderful diversity on the "small issues" (you should burn your dead vs. you should eat your dead).
The book is a whirling adventure, jumping from large philosophical points, to evolutionary speculations, to economic theory, psychological studies, linquistics and more. I must admit I couldn't read the whole book because I got lost in the trees (I'm a forest man). But the book is taking part in an exciting branch of study, the "science of morality."
One philosophical point that books like this bring up is the different between explaining what morality is versus arguing what morality should be, or the "is" versus "ought" distinction. What do moral judgments look like in the brain? How did morality evolve? How do people normally act? These are trying to answer the "is" question, studied by neuroscience, evolutionary theory, and psychology. But then there's the "ought" people--the philosophers and theologians and moralists--who try to convince people how they should act, regardless of how things "are". These are the people who changed history. Sam Harris argues, in an interesting blurring of roles, that science (not philosophy or religion) ought to be spending more time on the ought questions.