What do these literary terms mean an sit quid sit and quomodo sit?

Answer 1

These are classifications for argumentation. An sit denotes and extant argument, such as whether or not something exists, or if it's true or false. Quid sit, sometimes also written as quit sit, denotes an argument of definition--what something is. Quo modo sit, I believe is related to Quale sit, which is an argument of quality or degree.

When arguing it is wise to proceed through these in order so that no false assumptions are made. For example, a logical progression would be. 1) I have a car; 2) it is a subcompact that is designed for economy and simplicity of ownership; and 3) compared with other models it costs slightly more, but tends to last longer so it is a "good" value.

This classical form of argument is similar to what we might today refer to as a claim.