用逆否命题检验推理方向？ 请指教

sdcar2010

Premise: If mathematical proposition, then cannot be proven true by observation.

Conclusion: If mathematical proposition, then one cannot know the proposition is true.

Assumption: If something cannot be proven true by observation, then one cannot know the proposition is true. Or to know something is true, one has to prove it true by observation. These two statements are contrapositive pairs.