把这一句，留给此刻的你

I had some hesitations about philosophy because, if you worked out a philosophical theory, it was hard to know whether you were going to be able to prove it or whether other theories had just as good a claim on belief.

我对哲学有些犹豫，因为，如果你提出一个哲学理论，你很难知道你是否能够证明它，或者其他理论是否有同样好的信仰主张。

— Stephen Cole Kleene 斯蒂芬·科尔·克莱恩