The Unity and Diversity of Natural Science

On the question of where the study of nature should begin, Aristotle’s teaching is clear and familiar. His first treatise on natural science, the Physics, tells us, at the very beginning, that the investigation of nature must

start from the things which are more knowable and certain to us and proceed towards those which are clearer and more certain in themselves; for the same things are not “knowable relatively to us” and “knowable” absolutely. So in the present inquiry we must follow this method and advance from what is more obscure by nature, but more certain to us, towards what is more certain and more knowable by nature.—Now what is to us plain and obvious at first is rather confused wholes, the elements and principles of which become known to us later by analysis. Thus we must advance from [vague] generalities to particulars. For it is a [vague] whole that is more known to sense perception, and a generality is likewise a kind of whole, comprising many things within it, like parts. Much the same happens in relation of the name to the definition. A name, such as “circle,” means vaguely a sort of whole: the definition analyses this whole into its parts [i.e. defining parts]. Similarly a child begins by calling all men “father,” and all women “mother,” but later on distinguishes each of them.¹

Should the thought occur to us that modern science may have rendered this mode of procedure obsolete, just as it has invalidated much of Aristotle’s cosmology, we shall find no support for our suspicion in one of the more advanced expositors of the scientific outlook, namely Lord Russell. Just last year, he wrote of a “prejudice” which he describes as “perhaps the most important in all my thinking.”

. . . This is concerned with method. My method invariably is to start from something vague but puzzling, something which seems indubitable but which I cannot express with any precision. I go through a process which is like that of first seeing something with the naked eye and then examining it through a microscope. I find that by fixity of attention divisions and distinctions appear where none at first was visible, just as through a microscope you can see the bacilli in impure water which without the microscope are not discernible. There are many who decry analysis, but it has seemed to me evident, as in the case of the impure water, that analysis gives new knowledge without destroying any of the previously existing knowledge. This applies not only to the structure of physical things, but quite as much to concepts. “Knowledge,” for example, as commonly used is a very imprecise term covering a number of different things and a number of stages from certainty to slight probability.

It seems to me that philosophical investigation, as far as I have experience of it, starts from that curious and unsatisfactory state of mind in which one feels complete certainty without being able to say what one is certain of. The process that results from prolonged attention is just like that of watching an object approaching through a thick fog: at first it is only a vague darkness, but as it approaches articulations appear and one discovers that it is a man or a woman, or a horse or a cow or what not. It seems to me that those who object to analysis would wish us to be content with the initial dark blur. Belief in the above process is my strongest and most unshakable prejudice as regards the methods of philosophical investigation.²

Now, what can such a mode of procedure have to do with our question, which is where we ought to begin a study of nature? The method described means that we should begin with generalities which, though vague, are quite certain. Of course no intellect with a speculative vitality can rest in these generalities however reassuring in their certainty. The mind wants to know as much as it can about as much as there is to know. Knowledge, as we progress, must...