This arrangement of the sciences and the Law of the Three States are together explanatory of the course of human thought and knowledge. They are thus the double key of Comte's systematisation of the philosophy of all the sciences from mathematics to physiology, and his analysis of social evolution, which is the basis of sociology. Each science contributes its philosophy. The co-ordination of all these partial philosophies produces the general Positive Philosophy. 'Thousands had cultivated science, and with splendid success; not one had conceived the philosophy which the sciences when organised would naturally evolve. A few had seen the necessity of extending the scientific method to all inquiries, but no one had seen how this was to be effected.... The Positive Philosophy is novel as a philosophy, not as a collection of truths never before suspected. Its novelty is the organisation of existing elements. Its very principle implies the absorption of all that great thinkers had achieved; while incorporating their results it extended their methods.... What tradition brought was the results; what Comte brought was the organisation of these results. He always claimed to be the founder of the Positive Philosophy. That he had every right to such a title is demonstrable to all who distinguish between the positive sciences and the philosophy which co-ordinated the truths and methods of these sciences into a doctrine' (_G. H. Lewes_). We may interrupt our short exposition here to remark that Comte's classification of the sciences has been subjected to a vigorous criticism by Mr. Herbert Spencer. Mr. Spencer's two chief points are these:--(1) He denies that the principle of the development of the sciences is the principle of decreasing generality; he asserts that there are as many examples of the advent of a science being determined by increasing generality as by increasing speciality. (2) He holds that any grouping of the sciences in a succession gives a radically wrong idea of their genesis and their interdependence; no true filiation exists; no science develops itself in isolation; no one is independent, either logically or historically. M. Littré, by far the most eminent of the scientific followers of Comte, concedes a certain force to Mr. Spencer's objections, and makes certain secondary modifications in the hierarchy in consequence, while still cherishing his faith in the Comtist theory of the sciences. Mr. Mill, while admitting the objections as good, if Comte's arrangement pretended to be the only one possible, still holds that arrangement as tenable for the purpose with which it was devised. Mr. Lewes asserts against Mr. Spencer that the arrangement in a series is necessary, on grounds similar to those which require that the various truths constituting a science should be systematically co-ordinated, although in nature the phenomena are intermingled.