“When a man tells you that he knows the exact truth about anything, you are safe in inferring that he is an inexact man. Every careful measurement in science is always given with the probable error, which is a technical term, conveying a precise meaning. It means: that amount of error which is just as likely to be greater than the actual error as to be less. It is characteristic of those matters in which something is known with exceptional accuracy that, in them, every observer admits that he is likely to be wrong, and knows about how much wrong he is likely to be. In matters where the truth is not ascertainable, no one admits that there is the slightest possibility of even the minutest error in his opinions. Who ever heard of a theologian prefacing his creed, or a politician concluding his speeches, with a statement as to the probable error in his opinions? It is an odd fact that subjective certainty is inversely proportional to objective certainty. The less reason a man has to suppose himself in the right, the more vehemently he asserts that there is no doubt whatever that he is exactly right. It is a practice of theologians to laugh at science because it changes. ‘Look at us,’ they say. ‘What we asserted at the Council of Nicea we still assert; whereas what the scientists asserted only two or three years ago is already forgotten and antiquated.’ Men who speak in this way have not grasped the great idea of successive approximations. No man who has the scientific temper asserts that what is now believed in science is exactly right; he asserts that it is a stage on the road towards the exact truth. When a change occurs in science, as, for example, from Newton’s law of gravitation to Einstein’s, what had been done is not overthrown, but is replaced by something slightly more accurate. Suppose you measured yourself with a rough apparatus, and came to the conclusion that you were 6ft. tall: you would not suppose, if you were wise, that your height was exactly 6 ft., but rather that your height was (say) between 5 ft. 11 in. and 6 ft. 1 in.; and if a very careful measurement showed that your height was (within a tenth of an inch) 5 ft. 11 9/10 in. you would not consider that that had overthrown the previous result. The previous result was that your height was about six feet , and this remains true. The case with the changes in science is precisely analogous.”
The full book can be found here.
thejqcorner 