I can compose counterpoint because I studied Palestrina in school and listened to much of his music, and I know a guy that can compose jazz. That sentence may seem to have absolutely nothing to do with the subject of epistemology, but it is true. That, in and of itself, makes it an interesting thing in regards to how we know and how we communicate truth. But that is not my purpose in using it. I used it because it communicates three distinct types of knowledge that every person has.
First, the sentence reflects that a person can have propositional knowledge. Propositional knowledge can be loosely defined as the type of knowledge that is stated in declarative or indicative statements and seeks to express a statement of fact or state of affairs. Generally a statement can be evaluated to determine if it contains a fact by restating as a “that” sentence. So, my statement “I can compose counterpoint” could be restated as “I know that I can compose counterpoint.” This reflects a statement of fact out the current state of my mental capabilities. If we were to put a simple label on propositional knowledge it would be that it is knowledge-that.
Second, our test sentence reflects that I have know-how. Know-how can best be described as ability. It is a knowledge that is gained not through propositional statements of fact but by skill acquisition. In this case the study of counterpoint involved learning rules, but it also involved learning the “feel” or “sound” of a particular type of music. I can describe propositionally the proper rules of counterpoint, but there is also a part of the composing process that is not easily described that came from listening to the music of Palestrina. One could compare this type of knowledge to the skill of being able to ride a bike. Most of us can do it, but not many of us could adequately describe to someone else how to do it.
The third type of knowledge that we can have is knowledge by acquaintance. This is encapsulated in my statement that “I know a guy that can compose jazz.” My knowledge of this particular person is a not a direct knowledge or a knowledge of my own mental state. Rather it is a a knowledge that comes from familiarity. In much the same way we could state that we know our spouse or our children. I don’t know my wife in the same way that she knows herself through her own perceptions and mental states, but I am familiar with her attitudes, demeanor, and appearance.
Of the three types of knowledge the one that concerns epistemologists the most is propositional knowledge. When someone claims that something is true that claim normally revolves around a statement of fact. Thus the search for truth and a definition of what knowledge really is must delve deeply into what propositional knowledge is.