“Everything is vague to a degree you do not realize till you have tried to make it precise.”

“If an opinion contrary to your own makes you angry, that is a sign that you are subconsciously aware of having no good reason for thinking as you do.”

“None of our beliefs are quite true; all have at least a penumbra of vagueness and error.”

“The methods of increasing the degree of truth in our beliefs are well known; they consist in hearing all sides, trying to ascertain all the relevant facts, controlling our own bias by discussion with people who have the opposite bias, and cultivating a readiness to discard any hypothesis which has proved inadequate.”

“Philosophy arises from an unusually obstinate attempt to arrive at real knowledge. What passes for knowledge in ordinary life suffers from three defects: it is cocksure, vague and self-contradictory. The first step towards philosophy consists in becoming aware of these defects, not in order to rest content with a lazy scepticism, but in order to substitute an amended kind of knowledge which shall be tentative, precise and self-consistent.”

“The Ten Commandments that, as a teacher, I should wish to promulgate, might be set forth as follows:1- Do not feel absolutely certain of anything.2- Do not think it worth while to proceed by concealing evidence, for the evidence is sure to come to light.3- Never try to discourage thinking for you are sure to succeed.4- When you meet with opposition, even if it should be from your husband or your children, endeavor to overcome it by argument and not by authority, for a victory dependent upon authority is unreal and illusory.5- Have no respect for the authority of others, for there are always contrary authorities to be found.6- Do not use power to suppress opinions you think pernicious, for if you do the opinions will suppress you.7- Do not fear to be eccentric in opinion, for every opinion now accepted was once eccentric.8- Find more pleasure in intelligent dissent than in passive agreement, for, if you value intelligence as you should, the former implies a deeper agreement than the latter.9- Be scrupulously truthful, even if the truth is inconvenient, for it is more inconvenient when you try to conceal it.10- Do not feel envious of the happiness of those who live in a fool’s paradise, for only a fool will think that it is happiness.”

“Intelligibility or precision: to combine the two is impossible.”