His way of teaching was to present you with things that had not yet been proved, and with all kinds of things which might turn out to have a counterexample, and sometimes unsolved problems - that is, unsolved by anyone, not only unsolved by you.
Ang kanyang paraan ng pagtuturo ay sa kasalukuyan ka sa mga bagay-bagay na may hindi pa na-proved, at sa lahat ng uri ng mga bagay-bagay na maaaring lumitaw na magkaroon ng isang counterexample, at kung minsan walang lutas problema - iyon ay, walang lutas ng kahit sino, hindi lamang sa pamamagitan ng walang lutas mo.