Deductive Logic Quotes

Men of learning began to set experiments aside...to form theories...and to substitute these in the place of experiments.

Mathematics, in its widest significance, is the development of all types of formal, necessary, deductive reasoning.

Facts - behind them lies the whole fabric of deductive truth.

Before I met Ayn Rand, I was a logical positivist, and accordingly, I didn't believe in absolutes, moral or otherwise. If I couldn't prove a proposition with facts and figures, it was without merit.

Although nature commences with reason and ends in experience it is necessary for us to do the opposite, that is to commence with experience and from this to proceed to investigate the reason.

I am delighted to know that Principia Mathematica can now be done by machinery. . . I am quite willing to believe that anything in deductive logic can be done by machinery.

Sometimes one must make extended conclusions from limited data.

There is nothing which an untrained mind shows itself more hopelessly incapable, than in drawing the proper general conclusions from its own experience. And even trained minds, when all their training is on a special subject, and does not extend to the general principles of induction, are only kept right when there are ready opportunities of verifying their inferences by facts.

The art of doing mathematics consists in finding that special case which contains all the germs of generality.

Without deductive logic science would be entirely useless. It is merely a barren game to ascend from the particular to the general, unless afterwards we can reverse the process and descend from the general to the particular, ascending and descending like angels on Jacob's ladder.

The physicist, in his study of natural phenomena, has two methods of making progress: (1) the method of experiment and observation, and (2) the method of mathematical reasoning. The former is just the collection of selected data; the latter enables one to infer results about experiments that have not been performed. There is no logical reason why the second method should be possible at all, but one has found in practice that it does work and meets with reasonable success.

This method of deduction ... is often called "combinatory". Its usefulness is not exhausted at this stage, but it does even at the outset lead to some valuable conclusions.

Inferences of Science and Common Sense differ from those of deductive logic and mathematics in a very important respect, namely, when the premises are true and the reasoning correct, the conclusion is only probable.

The mathematician starts with a few propositions, the proof of which is so obvious that they are called self-evident, and the rest of his work consists of subtle deductions from them. The teaching of languages, at any rate as ordinarily practiced, is of the same general nature authority and tradition furnish the data, and the mental operations are deductive.

Logicians may reason about abstractions. But the great mass of men must have images.

A single observation that is inconsistent with some generalization points to the falsehood of the generalization, and thereby 'points to itself'.

He did not arrive at this conclusion by the decent process of quiet, logical deduction, nor yet by the blinding flash of glorious intuition, but by the shoddy, untidy process halfway between the two by which one usually gets to know things.

Attention to detail - Sherlock certainly has that, and my memory is pretty good - but not as good as his.

From a drop of water a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other.