When the behaviourist observes the doings of animals, and decides whether these show knowledge or error, he is not thinking of himself as an animal, but as an at least hypothetically inerrant recorder of what actually happens. He "knows" that animals are deceived by mirrors, and believes himself to "know" that he is not being similarly deceived. By omitting the fact that he—an organism like any other—is observing, he gives a false air of objectivity to the results of his observation. As soon as we remember the possible fallibility of the observer, we have introduced the serpent into the behaviourist's paradise. The serpent whispers doubts, and has no difficulty in quoting scien­tific scripture for the purpose.

Scientific scripture, in its most canonical form, is embodied in physics (including physiology). Physics assures us that the occurrences which we call "perceiving objects" are at the end of a long causal chain which starts from the objects, and are not likely to resemble the objects except, at best, in certain very abstract ways. We all start from "naive realism", i.e., the doctrine that things are what they seem. We think that grass is green, that stones are hard, and that snow is cold. But physics assures us that the greenness of grass, the hardness of stones, and the coldness of snow, are not the greenness, hardness, and coldness that we know in our own experience, but something very dif­ferent. The observer, when he seems to himself to be observing a stone, is really, if physics is to be believed, observing the effects of the stone upon himself. Thus science seems to be at war with itself: when it most means to be objective, it finds itself plunged into subjectivity against its will. Naive realism leads to physics, and physics, if true, shows that naive realism is false. Therefore naive realism, if true, is false; therefore it is false. And therefore the behaviourist, when he thinks he is recording observations about the outer world, is really recording observations about what is happening in him.

 

Bretrand Russell. An Inquiry into Meaning and Truth. Unwin, 1980, p14 - 15.