Hypotheses Are What We Lack The Least.

If We Knew Exactly The Laws Of Nature And The Situation Of The Universe At The Initial Moment, We Could Predict Exactly The Situation Of The Same Universe At A Succeeding Moment.

Ideas Rose In Clouds; I Felt Them Collide Until Pairs Interlocked, So To Speak, Making A Stable Combination.

How Is Error Possible In Mathematics?

To Invent Is To Discern, To Choose.

The Advance Of Science Is Not Comparable To The Changes Of A City, Where Old Edifices Are Pitilessly Torn Down To Give Place To New, But To The Continuous Evolution Of Zoologic Types Which Develop Ceaselessly And End By Becoming Unrecognisable To The Common Sight, But Where An Expert Eye Finds Always Traces Of The Prior Work Of The Centuries Past. One Must Not Think Then That The Old-fashioned Theories Have Been Sterile And Vain.