Nay, even the grand discovery of all—­the law of gravitation—­depended for its proof upon an operation of physical science, the measurement of a degree on the Earth’s surface.  So completely indeed did it thus depend, that Newton had actually abandoned his hypothesis because the length of a degree, as then stated, brought out wrong results; and it was only after Picart’s more exact measurement was published, that he returned to his calculations and proved his great generalisation.  Now this constant intercommunion, which, for brevity’s sake, we have illustrated in the case of one science only, has been taking place with all the sciences.  Throughout the whole course of their evolution there has been a continuous consensus of the sciences—­a consensus exhibiting a general correspondence with the consensus of faculties in each phase of mental development; the one being an objective registry of the subjective state of the other.

From our present point of view, then, it becomes obvious that the conception of a serial arrangement of the sciences is a vicious one.  It is not simply that the schemes we have examined are untenable; but it is that the sciences cannot be rightly placed in any linear order whatever.  It is not simply that, as M. Comte admits, a classification “will always involve something, if not arbitrary, at least artificial;” it is not, as he would have us believe, that, neglecting minor imperfections a classification may be substantially true; but it is that any grouping of the sciences in a succession gives a radically erroneous idea of their genesis and their dependencies.  There is no “one rational order among a host of possible systems.”  There is no “true filiation of the sciences.”  The whole hypothesis is fundamentally false.  Indeed, it needs but a glance at its origin to see at once how baseless it is.  Why a series?  What reason have we to suppose that the sciences admit of a linear arrangement?  Where is our warrant for assuming that there is some succession in which they can be placed?  There is no reason; no warrant.  Whence then has arisen the supposition?  To use M. Comte’s own phraseology, we should say, it is a metaphysical conception.  It adds another to the cases constantly occurring, of the human mind being made the measure of Nature.  We are obliged to think in sequence; it is the law of our minds that we must consider subjects separately, one after another:  therefore Nature must be serial—­therefore the sciences must be classifiable in a succession.  See here the birth of the notion, and the sole evidence of its truth.  Men have been obliged when arranging in books their schemes of education and systems of knowledge, to choose some order or other.  And from inquiring what is the best order, have naturally fallen into the belief that there is an order which truly represents the facts—­have persevered in seeking such an order; quite overlooking the previous question whether it is likely that Nature has consulted the convenience of book-making.