Facts are constituted by older ideologies, and a clash between facts and theories may be proof of progress.

Science is an essentially anarchic enterprise.

The world we inhabit is abundant beyond our wildest imagination. There are trees, dreams, sunrises; there are thunderstorms, shadows, rivers; there are wars, flea bites, love affairs; there are the lives of people, Gods, entire galaxies. The simplest human action varies from one person and occasion to the next-how else would we recognize our friends only from their gait, posture, voice, and divine their changing moods? Only a tiny fraction of this abundance affects our minds. This is a blessing, not a drawback.

Those who violate the rules of a language do not enter new territory; they leave the domain of meaningful discourse. Even facts in these circumstances dissolve, because they are shaped by the language and subjected to its limitations.

The only absolute truth is that there are no absolute truths.

Unanimity of opinion may be fitting for a church, for the frightened or greedy victims of some (ancient, or modern) myth, or for the weak and willing followers of some tyrant. Variety of opinion is necessary for objective knowledge. And a method that encourages variety is also the only method that is comparable with a humanitarian outlook.

Copernicanism and other essential ingredients of modern science survived only because reason was frequently overruled in their past.