and make it tractable and tame to man’s uses.  All I teach depends upon my hypothesis.  In it is the secret of all the power I wield.  I do not pretend to say what this elemental energy is.  I make no declaration regarding the actual nature of things; and all questions as to the ultimate origin or final destination of the world are beyond the scope of my inquiry.  I am ruled by my hypothesis; I regard phenomena from my point of view; and my right to do so I substantiate by the practical and theoretical results which follow.”  The language of geology, chemistry, zoology, and even mathematics is the same.  They all start from a hypothesis; they are all based on an imaginative conception, and in this sense their votaries are poets, who see the unity of being throb in the particular fact.

Now, so far as the particular sciences are concerned, I presume that no one will deny the supreme power of these colligating ideas.  The sciences do not grow by a process of empiricism, which rambles tentatively and blindly from fact to fact, unguided of any hypothesis.  But if they do not, if, on the contrary, each science is ruled by its own hypothesis, and uses that hypothesis to bind its facts together, then the question arises, are there no wider colligating principles amongst these hypotheses themselves?  Are the sciences independent of each other, or is their independence only surface appearance?  This is the question which philosophy asks, and the sciences themselves by their progress suggest a positive answer to it.

The knowledge of the world which the sciences are building is not a chaotic structure.  By their apparently independent efforts, the outer kosmos is gradually reproduced in the mind of man, and the temple of truth is silently rising.  We may not as yet be able to connect wing with wing, or to declare definitely the law of the whole.  The logical order of the hypotheses of the various sciences, the true connection of these categories of constructive thought, may yet be uncertain.  But, still, there is such an order and connection:  the whole building has its plan, which becomes more and more intelligible as it approaches to its completion.  Beneath all the differences, there are fundamental principles which give to human thought a definite unity of movement and direction.  There are architectonic conceptions which are guiding, not only the different sciences, but all the modes of thought of an age.  There are intellectual media, “working hypotheses,” by means of which successive centuries observe all that they see; and these far-reaching constructive principles divide the history of mankind into distinct stages.  In a word, there are dynasties of great ideas, such as the idea of development in our own day; and these successively ascend the throne of mind, and hold a sway over human thought which is well-nigh absolute.