Why shouldn't we expect the cat that got the cream to purr like a kitten? It feels, too

This is a lively, shrewd, well-argued book on the simple theme that animals are able to feel pleasure. People new to the topic may be surprised that such an obvious fact should need arguing. But, as Jonathan Balcombe makes clear, this field has long been ruled by rather bizarre a priori theories: "During much of the 20th century, scientific thinking was gripped by a stifling 'behaviourist' dogma that rejected the idea of animals as conscious feeling beings. As a consequence, the recently prevailing attitude to the question of animal feelings was to either flatly deny them, or ignore them."

In its day, the behaviourist technique of ignoring subjectivity certainly saved investigators a lot of trouble. Its doctrines, which were invented to simplify the psychological scene by excluding the tiresome complications of experience, fell into disrepute in the human field because those complications proved too obtrusive to ignore. Even there, however, bewildered inquirers still find its simplifications tempting. And in animal studies, where misrepresented subjects cannot audibly protest, it was long allowed to rule the field almost completely. Eventually, however, people started to ask why so radical a distinction should be made between humans and other animals that behaviourism should work for one and not for the other. Since the Darwinian revolution, the reason for this ruling really has not been obvious. Charles Darwin himself wrote straightforwardly about animal feelings in The Expression of the Emotions in Man and Animals . And inquiries about the nervous systems involved have not revealed a difference drastic enough to explain it. Descartes, when he ruled that animals were simply unconscious automata, had not heard about those inquiries.

Despite, however, the objections of a few philosophers such as Montaigne, Bentham, Mill and Schopenhauer, plenty of theorists have followed Descartes, assuming as a default position that animals must actually be unconscious and laying a mysterious burden of proof on anyone who questioned this. And, until lately, even less extreme inquirers commonly assumed that any consciousness present was so rudimentary that it could be ignored in describing behaviour. So a whole euphemistic language was invented to describe it without imputing subjectivity. Animals do not show distress, merely "stress", which is neurological. They do not scream or cry or wail or growl or moan. They merely "vocalise".

Balcombe confronts this absurd situation ingeniously by concentrating on pleasure, a concept that inevitably opens up a wide psychological perspective. Animals, like people, unmistakably take pleasure in activities that suit them, and the resulting behaviour cannot be intelligibly described at all without reference to the range of feeling behind it. The highly speculative evolutionary explanations that are now so popular are no substitute for this crucial subjective element. Asking how a given species acquired a taste for something is entirely distinct from asking what now attracts individuals of that species towards it. Both questions can be answered. We badly need a much better balance between them, and Balcombe's book is an admirable contribution.

Mary Midgley was formerly senior lecturer in philosophy, Newcastle University.