This selection is adapted from Austin M. Woodbury, Logic, The John N. Deely and Anthony F. Russel Collection, St. Vincent College Library, Latrobe, PA, 120-121.
The general issue to be considered here are the instruments that logic furnishes for the the manifestation of truth, enabling us to proceed from a vague knowledge to a distinct knowledge. We should note here the pivotal role played in this by means definitions and divisions. These are often ignored even though they are what bring about the perfection of the first operation of the intellect. Nous has its own instruments or "procedures" for bringing clarity out of the nebulous cloud from which insight first emerges.
Notion of "Mode of Knowing"
First, we must consider what we mean by a "mode of knowing." At first, the human intellect knows nothing perfectly but, instead, has knowledges that are obscure, confused, or doubtful. To perfect its knowledge, the intellect uses logical instruments that we call "modes of knowing." For this reason, a mode of knowing is defined as, "A discourse that is manifestive of something that is unknown"—oratio alicuius ignoti manifestiva. Here, we do not mean by "unknown" that something is utterly unknown. Instead, we take "unknown" for obscure, confused, or doubtful.
Division of the Modes of Knowing
Now, we must consider the division of modes of knowing accepted by the Thomistic school. There are two sorts of unknowns that we may need to make manifest, namely something that is incomplex (simple) or something that is a complex truth. Now, with regard to incomplex things (which are the simple essence of a thing), manifestation occurs either (1) with regard to its constitution or (2) with regard to its parts. Its constitution is manifested by means of definitions, while it is manifested with regard to its parts by means of divisions. However, as regards a complex truth, i.e. the logical truth found only in judgments (which are logically complex), manifestation occurs by means of proof or argumentation.
Thus, there are are three modes of knowing, namely:
However, it is important to note that a term is not, of itself, a logical instrument (i.e. a mode of knowing), except in a remote manner. This is so because we do not bring our knowledge to perfection by means of terms by themselves. They only play a role in such perfecting of knowledge when they are conjoined to one another in some special way—i.e. inasmuch as definitions, divisions, or argumentations are formed from termsInasmuch as these latter three are the "modes of knowing" that we are discussing here (namely, with regard to the perfecting of human knowledge), they are the modes of knowing that we are concerned with here.
Also, we should note that sense experience, by which we know the truth of a fact is not a mode of knowing, for the truth of a fact known by sense experience does not need a medium whereby it is manifested.
Likewise, faith, by which something is believed on the testimony of a witness, is not a mode of knowledge because it does not manifest the thing itself but, instead, leave it obscure.
Finally, we can concede that logic itself is indeed a mode of knowing. However, it is only such ain a universal manner (given that it provides the universal instrument for directing human knowledge), but not in a specific manner.