All in the baby's mind

Steven Pinker's latest book is bigger and bolder than anything he has previously written. In The Language Instinct (1994), he treated readers to an enticing overview of modern linguistics. In How the Mind Works (1997), his theme was much broader, but it was still largely a matter of describing and arguing for scientific theories. Now, in The Blank Slate, Pinker has ventured beyond the borders of science altogether, into such different fields as history, ethics and philosophy.

Science is still central to the book, especially the disciplines which Pinker calls "the sciences of mind, brain, genes and evolution" (cognitive science, neuroscience, behavioural genetics and evolutionary psychology). In early chapters, Pinker briefly summarises the main findings of these disciplines and shows how they have effectively undermined the idea that human nature is infinitely flexible.

This idea - the "blank slate" of the title - can be traced back to John Locke, the 17th century English philosopher who thought that the mind of the newborn child was like "white paper void of all characters, without any ideas". This view, known as empiricism, eventually triumphed over the older theory, going back to Plato, that the newborn mind was already richly structured.

During the 20th century, the blank slate became orthodoxy in psychology and the social sciences. Only now are scientists realising that, in this respect at least, Plato was right all along. The mind of the infant is not a blooming, buzzing confusion - it is equipped with lots of highly specialised innate equipment.

The most famous piece of hardwired machinery is Chomsky's language-acquisition device, which Pinker described at length in The Language Instinct. Now, Pinker outlines many more special-purpose modules, from devices for understanding other minds, to modules for acquiring certain kinds of fears and food preferences and for recognising biological species. And this is just the tip of the iceberg. Judging by Pinker's list, the baby's mind is an exquisitely complex set of components.

But Pinker's main concern is no longer merely to expound and argue for particular scientific theories. This time, he is more interested in the social, political and philosophical implications of these theories. Pinker thinks that it is important to address these non-scientific issues because they often get in the way of a rational and clearheaded evaluation of the science.

He points out that many people tend to base their views about the truth or falsity of certain scientific theories not on the evidence for and against them, but on their supposed moral, political and philosophical consequences.

Such backwards reasoning is especially apparent when it comes to scientific theories about human nature. Take, for example, the idea that boys and girls are born with different mental aptitudes. For some feminists, this idea seems so politically dangerous that they are prepared to argue against it, whatever the evidence may be. Instead of starting out with an open mind and judging the idea according to the evidence, they proceed in the opposite direction. They want it to be false, and so conclude that it must be.

Pinker sets out to remedy the depressing tendency of many social scientists to engage in this particularly dishonest kind of wishful thinking. He does so by showing how many of the views that are commonly taken to have politically conservative consequences are, in fact, quite compatible with a politically correct, liberal democratic agenda. This whole argument, however, seems decidedly at odds with Pinker's contention that scientific theories must be judged purely on the factual evidence and not on their supposed political consequences. If the political and ethical consequences of a scientific theory are irrelevant to its truth-value, as Pinker claims at the start, there is simply no point in showing how you can be a politically correct evolutionary psychologist.

It would have been much more refreshing if, instead of trying to sweeten the pill of scientific truth by coating it with a smear of liberalism, Pinker had simply challenged his readers to swallow the pill of truth no matter how bitter it is.