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 THE GENERALISATIONS OF SCIENCE. 91 before the advent of man is, to say the least of it, somewhat con- fusing to plain scientific folk. In further illustration of the positive or scientific position we may take that law of biogenesis which Mr. Pearson also adduces in illustration of his position. This doctrine, as he says, is pro- bably accepted by ninety per cent, at least of scientific authorities ; and it admirably exemplifies the nature of a law of science. It is essentially a generalisation from experience. Beyond experience and legitimate inference founded thereupon it does not pretend to go. No scientific man who thoroughly knew what he was talk- ing about would, on the strength of this generalisation, dare to dogmatise from negative premisses and proclaim that nowhen and nowhere in the present or the past have living forms sprung into existence from not living antecedents. This would be a wholly illegitimate inference. Such a dogmatic assertion would probably come from one of strong theological bias, who had raised a plain scientific generalisation into a metaphysical law of nature, exer- cising in some mysterious way a mystic sway over facts. It is. not by restricting Natural Law to an observed uniformity that, we are most liable to fall into error ; but rather by illegitimately converting observed uniformity, true within the limits of observa- tion, true for finite time and space, and believed to be universally true under like conditions of experiment and observation, into a. metaphysical Natural Law, supposed to be true absolutely and without possible limitation. Now according to Mr. Pearson the law of biogenesis was in existence -at a time when most of the best authorities believed firmly in spontaneous generation, the existence of the law and our knowledge of it being, in his philosophy, totally different things. But when, I would ask, did the law begin to exist ? Did it exist before there were any phenomena over which it could exercise juris- diction? Or did it spring into existence with the advent of life. Let us, however, turn to other laws to press home these ques- tions. I presume that the inductions of Sociology may take rank as natural laws. I presume that, though we may not yet ade- quately know them, there are natural laws exercising jurisdiction over the phenomena special to social aggregates. But since when existent ? Have the laws been in some way evolved, pari passu,. with the phenomena? Were they pre-existent ? Or did they come into existence at some point of time during the continuous evolution of the phenomena ? These are matters on which I would gladly be informed. From the standpoint of positive science, however, this antithesis, between our knowledge of natural laws and their existence involves a serious misconception of the nature of scientific laws.. Such laws are essentially bits of knowledge, and except as known have no existence. In Berkeleyan phrase their esse is cognosd. An unknown scientific law is a contradiction in terms : it is a, generalisation that has never been reached.