Nomothetic work on the one side and systematics on the other do, in fact, appear in every natural science, and besides them there are no other main parts. But “science” as a whole stands apart from another aspect of reality which is called “history.” History deals with particulars, with particular events at such and such a place, whilst science always abstracts from the particular, even in its systematic half.[1] [1] Windelband (*Geschichte und Naturwissenschaft*, 3 Auflage, 1904) gives the name “nomothetic” to the whole of our “science” and calls the method of history “idiographic.” We thought it better to establish three fundamental types of all possible branches of knowledge. GENERAL PLAN OF THESE LECTURES Turning now to a sort of short outline of what is to be discussed in the whole of our future lectures, this summer and next, it seems clear, without further analysis, that biology as a science has its nomothetic and its systematic part also; respiration and assimilation, for instance, have proved to be types of natural laws among living phenomena, and that there is a “system” of animals and plants is too commonly known to require further explanation here. Therefore we might study first biological laws, and after that biological systematics, and in the third place perhaps biological history. But that would hardly correspond to the philosophical aims of our lectures: our chief object is not biology as a regular science, as treated in text-books and in ordinary university lectures; our chief object is the Philosophy of the Organism, as aided and supported by scientific biology. Therefore a general acquaintance with biology must be assumed in these lectures, and the biological materials must be arranged according to their bearing on further, that is on philosophical, analysis. That will be done, not, of course, to the extent of my regarding every one of my audience as a competent biologist; on the contrary, I shall explain most fully all points of biology proper, and even of the most simple and descriptive kind of biology, which serve as bases for philosophical analysis. But I shall do so only if they indeed do serve as such bases. All our biology will be not for its own sake, but for the sake of philosophy. Whilst regarding the whole of the biological material with such aims, it seems to me best to arrange the properly scientific material which is to be the basis of my discussions, not along the lines which biology as an independent science would select,[2] but to start from the three different kinds of fundamental phenomena which living bodies offer to investigation, and to attach all systematics exclusively to one of them. For there will not be very much for philosophy to learn from biological systematics at present. [2] See J. Arth. Thomson, *The Science of Life*, London, 1899.