I am reading the Trivium on classical education.  I noticed something about sentences that create collections or classes of things that are empty sets, i.e. which do not corresp0nd to something in reality.  I call them absurd sentences, as I do not know another term that fits.

There are two types of absurd sentences.  The first is analytically absurd, i.e. it refers to something intrinsically impossible.  Logical analysis can show its nullity.  An example is the square circle, the universe of numbers where 5<4 and 4<5, etc.  Sometimes pure mathematicians can speculate on worlds with such axioms, and come up with inferences of things and processes that might exist in such a world.  Such speculation is unlikely to be useful outside the pure mathematical analysis.

The next is synthetically absurd, i.e. referring to such things that happen not to exist in reality, but are not inherently impossible, e.g. the purple cow, the flying cat, the three moons of Earth.

This set of defects can be shown to be relevant into bad modern thought on such things as our healthcare system.  I may do so.