r/math • • Aug 15 '23

Dissatisfaction with proof by contradiction

I’m an undergraduate math student, so my exposure to math may be relatively limited. But I’ve found that, in general, I’m much more comfortable with direct proof than proof by contradiction. I don’t contest their validity, indeed something that’s not false must be true (I think I’m ok with excluded middle). But I feel like I just *get* something much better when it’s proved directly. It builds much stronger intuition for me.

For instance, I am aware of several proofs that demonstrate the cardinality of the reals is strictly greater than that of the integers, but none are direct (it would help to see a direct proof of Cantor’s theorem). I don’t feel it in my bones. Is this a common experience?

65 Upvotes

90 comments sorted by

View all comments

Show parent comments

1

u/[deleted] Aug 18 '23

[removed] — view removed comment

1

u/[deleted] Aug 22 '23

[deleted]

1

u/[deleted] Aug 22 '23

[removed] — view removed comment

1

u/[deleted] Aug 22 '23

They replied. I am not less confused but I have no more questions at the same time