In my intro to philosophy class, our teacher presented us with "Kant's revolutionary thesis":
There are synthetic a priori propositions. They must be [necessarily are] true without appealing to experience (i.e. they are a priori) yet the predicate is not logically contained within the subject (i.e. they are synthetic).
I assume Hume would not have accepted this but on what lines could he have replied to Kant? ...I may need a plain English explanation.