A learner may know that 12 is even without understanding a proof. Showing that every multiple of 4 is even, and that 12 is a multiple of 4, clarifies why. The status of a proposition as familiar should not be confused with having understood its justification. The book’s “unknown judgment” refers to what the proof is meant to establish for the learner.
Opening interactive controls...
What if the conclusion is already familiar?
Ḥujjah: Deriving a Conclusion from Known Judgments
A learner may know that 12 is even without understanding a proof. Showing that every multiple of 4 is even, and that 12 is a multiple of 4, clarifies why. The status of a proposition as familiar should not be confused with having understood its justification. The book’s “unknown judgment” refers to what the proof is meant to establish for the learner.