 The attraction of behaviourism, he reminds us, is simply that it does not insist on occult happenings as the basis upon which all mental terms are given meaning, and points to the perfectly observable criteria that are by and large employed when we are called upon to defend or correct our employment of these mental terms. The problem with behaviourism is that it has a too-narrow view both of what counts as behaviour and of what counts as observable. The attraction of Cartesianism is that it recognizes in a way the behaviourist does not that there may be crucial differences between creatures who—on a certain restrictive notion of behaviour—do indeed behave identically. The problem with Cartesianism is that it attempts to account for these differences by hypothesizing the existence of occult or hidden causes.