If Ideas Had Shapes

A quoteblog ranging from philosophers in bathrobes to galaxy-rises

Tag: rationality

Alan Lightman – Mr. g (2012)

“Do you think it is possible for a thing and its opposite both to be true?”

“A thing and its opposite cannot both be true in a rational system of thought,” I replied. “But rational thoughts lead only to rational thoughts, whereas irrational thoughts lead to—”

“New experiences.”


Ibn Warraq – Why I Am Not a Muslim (1995)

To answer “all is possible for God” is simply to admit the essential irrationality of the doctrine of reconstitution.

(quoted in The Portable Atheist)

Bertrand Russell – “An Outline of Intellectual Rubbish” (1950)

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. If some one maintains that two and two are five, or that Iceland is on the equator, you feel pity rather than anger, unless you know so little of arithmetic or geography that his opinion shakes your own contrary conviction. The most savage controversies are those about matters as to which there is no good evidence either way. Persecution is used in theology, not in arithmetic, because in arithmetic there is knowledge, but in theology there is only opinion. So whenever you find yourself getting angry about a difference of opinion, be on your guard; you will probably find, on examination, that your belief is going beyond what the evidence warrants.

(quoted in The Portable Atheist)

George Eliot – “Evangelical Teaching” (1855)

What is for them a state of emotion submerging the intellect is with him a formula imprisoning the intellect, depriving it of its proper function–the free search for truth–and making it the mere servant-of-all-work to a foregone conclusion. Minds fettered by this doctrine no longer inquire concerning a proposition whether it is attested by sufficient evidence, but whether it accords with Scripture; they do not search for facts, as such, but for facts that will bear out their doctrine…. It is easy to see that this mental habit blunts not only the perception of truth, but the sense of truthfulness, and that the man whose faith drives him into fallacies treads close upon the precipice of falsehood.

(quoted in The Portable Atheist)

David Hume – An Enquiry Concerning Human Understanding (1748)

“…no testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous, than the fact, which it endeavours to establish: And even in that case there is a mutual destruction of arguments, and the superior only gives us an assurance suitable to that degree of force, which remains, after deducting the inferior.”

quoted in The Portable Atheist

David Hume – An Enquiry Concerning Human Understanding (1748)

All effects follow not with like certainty from their supposed causes. Some events are found, in all countries and all ages, to have been constantly conjoined together: Others are found to have been more variable, and sometimes to disappoint our expectations; so that, in our reasonings concerning matter of fact, there are all imaginable degrees of assurance, from the highest certainty to the lowest species of moral evidence. A wise man, therefore, proportions his belief to the evidence.

Suppose, for instance, that the fact, which the testimony endeavours to establish, partakes of the extraordinary and the marvellous; in that case, the evidence, resulting from the testimony, admits of a diminution, greater or less, in proportion as the fact is more or less unusual.

quoted in The Portable Atheist

Charles Darwin – The Descent of Man (1871)

The judgment of the community will generally be guided by some rude experience of what is best in the long run for all the members; but this judgment will not rarely err from ignorance and weak powers of reasoning. Hence the strangest customs and superstitions, in complete opposition to the true welfare and happiness of mankind, have become all-powerful throughout the world….

How so many absurd rules of conduct, as well as so many absurd religious beliefs, have originated, we do not know; nor how it is that they have become, in all quarters of the world, so deeply impressed on the mind of men; but it is worthy of remark that a belief constantly inculcated during the early years of life, while the brain is impressible, appears to acquire almost the nature of an instinct; and the very essence of an instinct is that it is followed independently of reason.

Richard Dawkins – The God Delusion (2006)

The fact that a question can be phrased in a grammatically correct English sentence doesn’t make it meaningful, or entitle it to our serious attention.

Richard Dawkins – The God Delusion (2006)

I mean it as a compliment when I say that you could almost define a philosopher as someone who won’t take common sense for an answer.

Carl Sagan – Pale Blue Dot (1994)

It is sometimes said that scientists are unromantic, that their passion to figure out robs the world of beauty and mystery. But is it not stirring to understand how the world actually works — that white light is made of colors, that color is the way we perceive the wavelengths of light, that transparent air reflects light, that in so doing it discriminates among the waves, and that the sky is blue for the same reason that the sunset is red? It does no harm to the romance of the sunset to understand a little bit about it.