In order to be used as a single unit, the enormous sum integrated by a concept
has to be given the form of a single, specific, perceptual concrete, which will
differentiate it from all other concretes and from all other concepts. This is
the function performed by language. Language is a code of visual-auditory
symbols that serves the psycho-epistemological function of converting concepts
into the mental equivalent of concretes. Language is the exclusive domain and
tool of concepts. Every word we use (with the exception of proper names) is a
symbol that denotes a concept, i.e., that stands for an unlimited number of
concretes of a certain kind.