@justforthelulz—
It is about the principles of a logic of uncertainty.
Some Details: What is ordinarily taught in a course on logic is
assertoric logic, which only allows for propositions to be discernibly true or discernibly false. Sometimes one is exposed to a
modal logic, in which propositions are
necessarily true, or
necessarily false, or
possible. (Modal logic could also be used to describe behaviors that are
required,
forbidden, or
permissible, but that's another story.) In real life, we cannot be certain of most things, but some things that are neither discerned to be true nor discerned to be false are more plausible than others. In those cases, we normally try to use what is typically called “probability”, but would be better called “measures of probability”, which quantifies the plausibility of these propositions. But some very strong assumptions are required for that quantification, and some of those assumptions don't hold-up under ordinary circumstances. Without those assumptions, there are still various rules.