Saint Anselm
"For I do not seek to understand that I may believe, but I believe in order to understand. For this I believe -- that unless I believe, I should not understand."
[Proslogion I]
Averroes
"Knowledge is the conformity of the object and the intellect."
[Destructio Destructionum]
Francis Bacon
"The human understanding is like a false mirror, which, receiving rays irregularly, distorts and discolors the nature of things by mingling its own nature with it."
[Novum Organum, Aphorism 41]
Francis Bacon
"If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties."
[Advancement of Learning]
George Berkeley
"I have no reason for believing the existence of matter. I have no immediate intuition thereof: neither can I immediately, from any sensations, ideas, notions, actions or passions infer an unthinking, unperceiving, inactive substance - either by probable deduction or necessary consequence."
[Three Dialogues Between Hylas And Philonous]
Rene Descartes
"But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am, was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search."
[Discourse on Method]
Rene Descartes
"If you would be a real seeker after truth, you must at least once in your life doubt, as far as possible, all things."
[Discourse on Method]
Rene Descartes
"The first precept was never to accept a thing as true until I knew it as such without a single doubt."
[Le Discours de la Methode, I]
Epictetus
"Appearances to the mind are of four kinds. Things either are what they appear to be; or they neither are, nor appear to be; or they are, and do not appear to be; or they are not, and yet appear to be. Rightly to aim in all these cases is the wise man’s task."
[Discourses]
Carl Hempel
"The propositions of mathematics have, therefore, the same unquestionable certainty which is typical of such propositions as 'All bachelors are unmarried,' but they also share the complete lack of empirical content which is associated with that certainty: The propositions of mathematics are devoid of all factual content; they convey no information whatever on any empirical subject matter."
[On the Nature of Mathematical Truth]
Edmund Husserl
"Universal doubt cancels itself."
[The Crisis of European Sciences and Transcendental Phenomenology]
William James
"Objective evidence and certitude are doubtless very fine ideals to play with, but where on this moonlit and dream-visited planet are they found?"
[The Will to Believe]
Saul Kripke
"Proper names are rigid designators."
[Naming and Necessity]
Lao Tzu
"To know that you do not know is the best.
To pretend to know when you do not know is a disease."
[The Way of Lao-Tzu, 71]
Gottfried Leibnitz
"There are two kinds of truths: those of reasoning and those of fact. The truths of reasoning are necessary and their opposite is impossible; the truths of fact are contigent and their opposites are possible."
[Monadology]
John Locke
"No man's knowledge here can go beyond his experience."
[Essay Concerning Human Understanding]
Michel de Montaigne
"Nothing is so firmly believed as what is least known."
[Essays, bk. 1, ch. 32]
Plato
"Behold! Human beings living in an underground den... Like ourselves... They see only their own shadows, or the shadows of one another, which the fire throws on the opposite wall of the cave."
[The Republic, bk. VII, 515-B]
Plato
"If a person shows that such things as wood, stones, and the like, being many are also one, we admit that he shows the coexistence of the one and the many, but he does not show that the many are one or the one many; he is uttering not a paradox but a truism."
[Dialogues, Parmenides, 129]
Karl Popper
"The theory of knowledge which I wish to propose is a largely Darwinian theory of the growth of knowledge. From the amoeba to Einstein, the growth of knowledge is always the same: we try to solve our problems, and to obtain, by a process of elimination, something approaching adequacy in our tentative solutions."
[Objective Knowledge: An evolutionary approach]
Richard Rorty
"Truth is, to be sure, an absolute notion, in the following sense: 'true for me but not for you' and 'true in my culture but not in yours' are weird, pointless locutions. So is 'true then but not now.'"
[Truth and Progress]
Bertrand Russell
"I wish to propose for the reader's favourable consideration a doctrine which may, I fear, appear wildly paradoxical and subversive. The doctrine in question is this: that it is undesirable to believe a proposition when there is no ground whatever for supposing it true."
[On the Value of Scepticism]
Socrates
"I know nothing except the fact of my ignorance."
[From Diogenes Laertius. Lives of Eminent Philosophers, Bk. II, sec. 32]
Alfred Tarski
"The sentence 'snow is white' is true if, and only if, snow is white."
[The Semantic Conception of Truth]
