From Chapter One of Carroll Quigley's 1961 book, The Evolution of Civilizations. Quigley's topic is the scientific method:
Having gathered all the "relevant" evidence, the scientist may proceed to the second part of scientific methodology, making a hypothesis. In doing this, two rules must be followed: (a) the hypothesis must explain all the observations and (b) the hypothesis must be the simplest one that will explain them.
The second rule, simplicity, is often called Occam's Razor.
The rule of simplicity or economy in scientific hypothesis has a number of corollaries. One of these, called "the uniformity of nature," assumes that the whole universe is made of the same substances and obeys the same laws and, accordingly, will behave in the same way under the same conditions. Such an assumption does not have to be proved—indeed, it could not be proved. It is made for two reasons. First, because it is simpler to assume that things are the same than it is to assume that they are different. And, second, while we cannot prove this assumption to be correct even if it is correct, we can, if it is not correct, show this by finding a single exceptional case.
Quigley continues:
We could demonstrate the uniformity of nature only by comparing all parts of the universe with all other parts, something that clearly could never be achieved. But we can assume this, because it is a simpler hypothesis than its contrary; and, if it is wrong, we can show this error by producing one case of a substance or a physical law that is different in one place or time from other places or times...
Thus, in the final analysis, these rules about scientific hypotheses are not derived from any sense of economy or of esthetics, but rather arise from the nature of demonstration and proof. The familiar judicial rule that a man is to be assumed innocent until he has been proved guilty is based on the same fundamental principles as these rules about scientific hypotheses, and, like these, rests ultimately on the nature of proof.
We must assume that a man is innocent (not guilty) until we have proof of his guilt because it is always simpler to assume that things are not so than to assume that they are, and also because no man can prove the negative "not guilty" except by the impossible procedure of producing proof of innocence during every moment of his past life. (If he omits a moment, the charge of guilt could then be focused on the period for which proof of innocence is unobtainable.) But by making the general and negative assumption of innocence for all men, we can disprove this for any single man by the much easier procedure of producing evidence of guilt for a single time, place, and deed. Since it is true that a general negative cannot be demonstrated, we are entitled to make that general negative assumption under the rule of the simplicity of scientific hypothesis, and to demand refutation of such an assumption by specific positive proof.
A familiar example of this method could be seen in the fact that we cannot be required to prove that ghosts and sea serpents and clairvoyance do not exist. Scientifically we assume that these things do not exist, and require no evidence to justify this assumption, while the burden of producing proofs must fall on anyone who says that such things do exist.
Keynes's General Theory was published in 1936. Late in 1936, the Quarterly Journal of Economics presented responses to Keynes's book from Professor Taussig, Mr. Leontief, Mr. Robertson, and Professor Viner. Keynes, in turn, responded in the February 1937 issue of the Journal. The following is part of his response:
Mr. Leontief is right, I think, in the distinction he draws between my attitude and that of the "orthodox" theory to what he calls the "homogeneity postulate." I should have thought, however, that there was abundant evidence from experience to contradict this postulate; and that, in any case, it is for those who make a highly special assumption to justify it, rather than for one who dispenses with it, to prove a general negative.
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