Every Genuine Test Of A Theory Is

It Is Part Of My Thesis That All Our Knowledge Grows Only Through The Correcting Of Our Mistakes.

Every Solution Of A Problem Raises New Unsolved Problems.

If You Can't Say It Simply And Clearly, Keep Quiet, And Keep Working On It Till You Can.

No Particular Theory May Ever Be Regarded As Absolutely Certain.... No Scientific Theory Is Sacrosanct.

Psychologism Is, I Believe, Correct Only In So Far As It Insists Upon What May Be Called 'methodological Individualism' As Opposed To 'methodological Collectivism'; It Rightly Insists That The 'behaviour' And The 'actions' Of Collectives, Such As States Or Social Groups, Must Be Reduced To The Behaviour And To The Actions Of Human Individuals. But The Belief That The Choice Of Such An Individualist Method Implies The Choice Of A Psychological Method Is Mistaken.