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Since reasoning, or inference, the principal subject of logic, is an operation which usually takes place by means of words, and in complicated cases can take place in no other way: those who have not a thorough insight into both the signification and purpose of words, will be under chances, amounting almost to certainty, of reasoning or inferring incorrectly.
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p.11: Cited in Gaines (1976) "Foundations of fuzzy reasoning" in: International Journal of Man-Machine Studies 8(6), p. 623

 

John Stuart Mill

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To those who inquire as to the purpose of mathematics, the usual answer will be that it facilitates the making of machines, the travelling from place to place, and the victory over foreign nations, whether in war or commerce. ... The reasoning faculty itself is generally conceived, by those who urge its cultivation, as merely a means for the avoidance of pitfalls and a help in the discovery of rules for the guidance of practical life.

 

Bertrand Russell

 

We know truth, not only by the reason, but also by the heart, and it is in this last way that we know first principles; and reason, which has no part in it, tries in vain to impugn them. The sceptics, who have only this for their object, labour to no purpose. We know that we do not dream, and however impossible it is for us to prove it by reason, this inability demonstrates only the weakness of our reason, but not, as they affirm, the uncertainty of all our knowledge. For the knowledge of first principles, as space, time, motion, number, is as sure as any of those which we get from reasoning. And reason must trust these intuitions of the heart, and must base them on every argument. (We have intuitive knowledge of the tri-dimensional nature of space, and of the infinity of number, and reason then shows that there are no two square numbers one of which is double of the other. Principles are intuited, propositions are inferred, all with certainty, though in different ways.) And it is as useless and absurd for reason to demand from the heart proofs of her first principles, before admitting them, as it would be for the heart to demand from reason an intuition of all demonstrated propositions before accepting them.
This inability ought, then, to serve only to humble reason, which would judge all, but not to impugn our certainty, as if only reason were capable of instructing us. Would to God, on the contrary, that we had never need of it, and that we knew everything by instinct and intuition! But nature has refused us this boon. On the contrary, she has given us but very little knowledge of this kind; and all the rest can be acquired only by reasoning.
Therefore, those to whom God has imparted religion by intuition are very fortunate, and justly convinced. But to those who do not have it, we can give it only by reasoning, waiting for God to give them spiritual insight, without which faith is only human, and useless for salvation.

 

Blaise Pascal

 

I am not the advocate of Slavery, Caste, and Hatred, nor do I deny that a sense may be given to the words, Liberty, Equality, and Fraternity, in which they may be regarded as good. I wish to assert with respect to them two propositions.
First, that in the present day even those who use those words most rationally — that is to say, as the names of elements of social life which, like others, have their advantages and disadvantages according to time, place, and circumstance — have a great disposition to exaggerate their advantages and to deny the existence, or at any rate to underrate the importance, of their disadvantages.
Next, that whatever signification be attached to them, these words are ill-adapted to be the creed of a religion, that the things which they denote are not ends in themselves, and that when used collectively the words do not typify, however vaguely, any state of society which a reasonable man ought to regard with enthusiasm or self-devotion.

 

James Fitzjames Stephen

 

‘The Spirit of the Age wishes to allow argument and not to allow argument. … If anyone argues with them they say that he is rationalizing his own desires, and therefore need not be answered. But if anyone listens to them they will then argue themselves to show that their own doctrines are true. … You must ask them whether any reasoning is valid or not. If they say no, then their own doctrines, being reached by reasoning, fall to the ground. If they say yes, then they will have to examine your arguments and refute them on their merits: for if some reasoning is valid, for all they know, your bit of reasoning may be one of the valid bits.’

 

C. S. Lewis

 

Words that do not create images should be discarded. Words that have no intrinsic emotional or visual content ought to be avoided. Words that are directed to the sterile intellectual head-place should be abandoned. Use simple words, words that create pictures and action and that generate feeling.

 

Gerry Spence