The philosophy of life can not be any mere science of reason, and least of all an unconditional one. For such does but lead us into a domain of dead abstractions alien to life, which, by the dialectical spirit of disputation connatural to the reason, is soon converted into a labyrinthine maze of contradictory opinions and notions, out of which the reason, with all its logical means and appliances, can not extricate itself. And life, consequently--the inner spiritual life, that is--is disturbed and destroyed by it. And it is even this disturbing and destroying principle of the dialectical reason that most requires to be got rid of and brought into subjection. In the mere form, however, of abstract thought there is nothing in and by itself opposed to the truth. There is nothing in it that it is absolutely and invariably necessary to avoid, or that never and in no case admits of application. It is, no doubt, most certain that every system of philosophy is on a wrong track which borrows its method exclusively from mathematics, and copies it throughout from beginning to end. Still, in the progressive development of philosophical ideas certain points may occur--there may be certain places in the entire system--where occasionally and by the way such formulas and abstract equations may be profitably employed. Such a case may happen in the present Lecture. But by thus employing them only by way of illustration, and episodically in passing, I hope to establish such a use of them, and to make it evident that the perspicuity of the exposition does not essentially suffer thereby. Philosophy, as the universal science, embraces in its consideration the whole man. As, therefore, it evidently involves the occasion, so it is not unlikely that cases may occur where it can happily borrow, now from one now from another of the sciences, its external form and peculiar formularies. It can, in short, advantageously avail itself of all in turn. Only, such a use, to be profitable, must be free. And this freedom will best evince itself in the deliberate choice and the diversity of the images. The method of free speculation, _i.e._, of philosophy, must not resemble a coat of mail with its infinite number of little uniform chains and rings. It ought not, as is the case nearly with the mathematical method, to be composed, by mechanical rule and measure, of simple propositions scientifically linked together, and then formed again into higher logical concatenations. In short, the method of philosophy can not properly be uniform. The spirit must not be made subservient to the method; the essence must not be sacrificed to the form.