[stevegalla]

Broadly speaking, math is made up of theorems. The goal is to prove the theorem by establishing a proof, or disprove the theorem using a counterexample.

In math textbooks and courses I’ve had, there tends to be footnotes on who produced some foundational result (statement of the theorem, proof, or counterexample). So you study or learn about the original work, but you’re not doing so from the primary source (original work).

This could be because the proof of original work was: - in a different language, - required advanced knowledge the learner doesn’t have, - a more simplified proof was found, - a more enlightening proof was found, - an informal proof suffices, - the statement of the theorem is all that’s needed, - the proof is left as an exercise to the reader, - the proof is a special case of a more general proof, - or any number of other reasons