Full Idea
One philosopher's modus ponens is another philosopher's modus tollens.
Gist of Idea
My modus ponens might be your modus tollens
Source
Duncan Pritchard (Epistemological Disjunctivism [2012], 3.§2)
Book Reference
Pritchard,Duncan: 'Epistemological Disjunctivism' [OUP 2012], p.114
A Reaction
[Anyone know the originator of this nice thought?] You say A is true, and A proves B, so B is true. I reply that if A proves something as daft as B, then so much the worse for A. Ain't it the truth?