ABSTRACT
It was Aristotle who first defined a human being as a rational animal, and he meant by this that humans were to be distinguished from other animals in that they had the ability to think, calculate or reason. 1 Other animals can respond to their environment; they can sense the heat from flames, for example, and withdraw from the fire. Instinctively they can seek shelter in appropriate places from bad weather or from enemies. Not only do they respond in a regular manner to specific signals, but they can also be conditioned by humans to respond to artificial signals. The wild animal senses its prey and automatically responds with the appropriate hunting behavior. The dog, taken over as a household pet, automatically responds to certain food-preparing activities on the part of the owner. In extreme cases, as in Pavlov’s experiments, the animal is conditioned to respond to signals such as the ringing of a bell. But what animals cannot do is act purposively. They cannot decide to do this rather than that on certain grounds, they cannot work out what is going on, or reflect upon the possibility that the ringing bells may be part of some experiment on their behavior. Humans differ from other animals in that they are able to act purposively, to plan, choose ends and adopt means, and in that they are able to control their environment rather than simply respond to it. They are able to memorize, to imagine, foresee, to predict, to hypothesize. To use the imprecise term which in common language includes all such activities, humans have the capacity to think. (See Chapter 3.)
