A Very Small Cause, Which Escapes Us,

All That Is Not Thought Is Pure Nothingness; Since We Can Think Only Thoughts, And All The Words We Use To Speak Of Things Can Express Only Thoughts, To Say There Is Something Other Than Thought Is Therefore An Affirmation Which Can Have No Meaning.

What Is A Good Definition? For The Philosopher Or The Scientist, It Is A Definition Which Applies To All The Objects To Be Defined, And Applies Only To Them; It Is That Which Satisfies The Rules Of Logic. But In Education It Is Not That; It Is One That Can Be Understood By The Pupils.

I Entered An Omnibus To Go To Some Place Or Other. At That Moment When I Put My Foot On The Step The Idea Came To Me, Without Anything In My Former Thoughts Seeming To Have Paved The Way For It, That The Transformations I Had Used To Define The Fuchsian Functions Were Identical With Non-euclidean Geometry.

But All Of My Efforts Served Only To Make Me Better Acquainted With The Difficulty, Which In Itself Was Something.

A Sane Mind Should Not Be Guilty Of A Logical Fallacy, Yet There Are Very Fine Minds Incapable Of Following Mathematical Demonstrations.