Ordinarily Pleasure And Pain Are Regarded As

A Colour Is A Physical Object As Soon As We Consider Its Dependence, For Instance, Upon Its Luminous Source, Upon Other Colours, Upon Temperatures, Upon Spaces, And So Forth.

The Mathematician Who Pursues His Studies Without Clear Views Of This Matter, Must Often Have The Uncomfortable Feeling That His Paper And Pencil Surpass Him In Intelligence.

Thought Experiment Is In Any Case A Necessary Precondition For Physical Experiment. Every Experimenter And Inventor Must Have The Planned Arrangement In His Head Before Translating It Into Fact.

Many An Article That I Myself Penned Twenty Years Ago Impresses Me Now As Something Quite Foreign To Myself.

The Task Which We Have Set Ourselves Is Simply To Show Why And For What Purpose We Hold That Standpoint During Most Of Our Lives, And Why And For What Purpose We Are Provisionally Obliged To Abandon It.