“We prove what we want to prove, and the real difficulty is to know what we want to prove.”
Alain (1868–1951) French philosopher
On prouve tout ce qu'on veut, et la vraie difficulté est de savoir ce qu'on veut prouver.
Système des Beaux-Arts (1920), as quoted in The Most Brilliant Thoughts of All Time (In Two Lines or Less) by John M. Shanahan, p. 34
Variant translation: We prove anything we want to prove, and the real difficulty is to know what we want to prove.