Nicene and Post-Nicene Fathers, Vol. II:
On Christian Doctrine: Chapter 35

Chapter 35 .—The Science of Definition is Not False, Though It May Be Applied to Falsities.

53.  Again, the science of definition, of division, and of partition, although it is frequently applied to falsities, is not itself false, nor framed by man’s device, but is evolved from the reason of things.  For although poets have applied it to their fictions, and false philosophers, or even heretics—that is, false Christians—to their erroneous doctrines, that is no reason why it should be false, for example, that neither in definition, nor in division, nor in partition, is anything to be included that does not pertain to the matter in hand, nor anything to be omitted that does.  This is true, even though the things to be defined or divided are not true.  For even falsehood itself is defined when we say that falsehood is the declaration of a state of things which is not as we declare it to be; and this definition is true, although falsehood itself cannot be true.  We can also divide it, saying that there are two kinds of falsehood, one in regard to things that cannot be true at all, the other in regard to things that are not, though it is possible they might be, true.  For example, the man who says that seven and three are eleven, says what cannot be true under any circumstances; but he who says that it rained on the kalends of January, although perhaps the fact is not so, says what posssibly might have been.  The definition and division, therefore, of what is false may be perfectly true, although what is false cannot, of course, itself be true.