Ayn Rand & Epistemology 25

Definitions 10: Doctrine of Ostensive Definition. In my last post, I noted that definitions lead to an infinite regress. Once a word has been defined, then you need to define the words used in the definition. But the words of those definitions need to be defined as well; and this process must go on forever. How does Objectivism propose to evade this infinite regress? Through their theory of ostensive definition. Rand introduces it as follows:

With certain significant exceptions, every concept can be defined and communicated in terms of other concepts. The exceptions are concepts referring to sensations, and metaphysical axioms.

Sensations are the primary material of consciousness and, therefore, cannot be communicated by means of the material which is derived from them. The existential causes of sensations can be described and defined in conceptual terms (e.g., the wavelengths of light and the structure of the human eye, which produce the sensations of color), but one cannot communicate what color is like, to a person who is born blind. To define the meaning of the concept “blue,” for instance, one must point to some blue objects to signify, in effect: “I mean this.” Such an identification of a concept is known as an “ostensive definition.”

Ostensive definitions are usually regarded as applicable only to conceptualized sensations. But they are applicable to axioms as well. Since axiomatic concepts are identifications of irreducible primaries, the only way to define one is by means of an ostensive definition—e.g., to define “existence,” one would have to sweep one’s arm around and say: “I mean this.”

Ayn Rand & Epistemology 24

Definitions 9: Doctrine of Verbalism. Rand is very clear on the relation between knowledge and definitions:

The truth or falsehood of all of man’s conclusions, inferences, thought and knowledge rests on the truth or falsehood of his definitions. [IOTE, 49]

Definitions are the guardians of rationality, the first line of defense against the chaos of mental disintegration. [RM, 77]

There is a serious problem with the Objectivist view of definitions that neither Rand nor her followers have ever adequately answered. The truth and falsehood of man's knowledge cannot possibly rest on definitions, because definitions are ultimately circular. One word is merely defined by other words; so that to expect to find truth and rationality in definitions is to expect what can never be found. As Karl Popper explained in The Open Society and Its Enemies: