Hallucinations do not Negate the Validity of the Senses

Hallucinations and dreams are often cited in an attempt to negate the validity of the senses as argued by the Objectivist epistemology. Those who do this citing are mistaken: that under certain circumstances a man is able to turn his attention away from the integration of percepts does not demonstrate that he is able to do nothing but this. That man can be deluded does not demonstrate that man is metaphysically deluded. In fact, the opposite is true. For a man to dream of, say, a pink elephant, he must first have the concepts "pink" and "elephant," for him to have acquired these concepts he must have abstracted the relevant details from particular instances of pink things and elephants. Such dreams and hallucinations do not, therefore, demonstrate that man is able to gain knowledge by mystic insight, or that he is born with innate ideas.

Once a mind acquires a certain content of sensory material, it can, as in the case of dreams, contemplate its own content rather than external reality. This is not sense perception at all, but a process of turning inward, made possible by the fact that the individual, through perception, first acquired some sensory contents. Nor, as Aristotle observed, is there any difficulty in distinguishing dreams from perception. The concept of "dream" has meaning only because it denotes a contrast to wakeful awareness. If a man were actually unable to recognize the latter state, the word "dream" to him would be meaningless.^[1]