This is mathematical induction, not weasel words. 1. If X grains is not a heap, X+1 grains is not a heap. 2. 1 grain is not a heap. You might disagree with 1

This is mathematical induction, not weasel words. 1. If X grains is not a heap, X+1 grains is not a heap. 2. 1 grain is not a heap. You might disagree with 1 (or 2, though normally we'd disagree with one), but "and so on" isn't weaseling. It's plainly expressing the recursive applicability of 1.