Obviousness Is Always The Enemy Of Correctness.

When One Admits That Nothing Is Certain One Must, I Think, Also Admit That Some Things Are Much More Nearly Certain Than Others.

All That Passes For Knowledge Can Be Arranged In A Hierarchy Of Degrees Of Certainty, With Arithmetic And The Facts Of Perception At The Top.

I've Always Thought Respectable People Scoundrels, And I Look Anxiously At My Face Every Morning For Signs Of My Becoming A Scoundrel.

I Am Not Myself In Any Degree Ashamed Of Having Changed My Opinions.

Logic Must No More Admit A Unicorn Than Zoology Can.