I act with complete certainty. But this certainty is my own.
We learn by rearranging what we know.
I am my world.
Philosophy can be said to consist of three activities: to see the commonsense answer, to get yourself so deeply into the problem that the common sense answer is unbearable, and to get from that situation back to the commonsense answer.
Don't ask what it means, but rather how it is used.
Whereof one cannot speak, thereof one must be silent.