(42) In case the opposite of a thing is not known to us, because it has not as yet been discovered by or made known to us, nevertheless in such case we are fully justified in ascribing to the unknown opposite the qualities and characteristics diametrically opposed to the known opposite. The rule is this: "Whatever is affirmed of one of a pair of opposites must be denied to the other"; and " whatever is denied to the one, must be affirmed of the other." So true and infallible is this rule that it may be applied and employed as the basis of logical reasoning from the known to the unknown, for the purpose of discovering the latter.

(8) Unsound intellection is false understanding, not resting on a perception of the true nature of things.