[Consider the catch phrase:] “This may be good in theory, but it doesn’t work
in practice.” What is a theory? It is a set of abstract principles purporting
to be either a correct description of reality or a set of guidelines for man’s
actions. Correspondence to reality is the standard of value by which one
estimates a theory. If a theory is inapplicable to reality, by what standard
can it be estimated as “good”? If one were to accept that notion, it would
mean: a. that the activity of man’s mind is unrelated to reality; b. that the
purpose of thinking is neither to acquire knowledge nor to guide man’s actions.
(The purpose of that catch phrase is to invalidate man’s conceptual faculty.)