There can never be surprises in logic.

Nothing is so difficult as not deceiving oneself.

We feel that even if all possible scientific questions be answered, the problems of life have still not been touched at all.

It is an hypothesis that the sun will rise tomorrow: and this means that we do not know whether it will rise.

The so-called law of induction cannot possibly be a law of logic, since it is obviously a proposition with a sense.--Nor, therefore, can it be an a priori law.

Words are probes. Some reach very deep, some only to a little depth.

One often makes a remark and only later sees how true it is.