You ask me if I keep a notebook to record my great ideas. I've only ever had one.

You can't solve problems with the same thinking that caused them.

I believe that pipe smoking contributes to a somewhat calm and objective judgement in all human affairs.

Dear Posterity, If you have not become more just, more peaceful, and in general more sensible... then may the Devil take you!

Time and space are modes by which we think and not conditions in which we live.

From a certain temperature on, the molecules 'condense' without attractive forces; that is, they accumulate at zero velocity. The theory is pretty, but is there some truth in it.

As the area of light expands, so does the perimeter of darkness.