458 THE SCIENTIFIC MONTHLY
Let me ask any reader who is " keen enough on ilie different kinds of automobiles to be able to distinguish most of the makes as they are passed on the road, what marks he relies on for identifying each type of car? Is it not true that in most cases you depend upon one or a few very trivial things ? Color comes in ; but, on the whole, one finds himself giving less attention for identification purposes to this con* spicuous attribute than to others far less conspicuous. Just now the shape and color, not the name, of the manufacturer's plate placed on the radiator of so many machines, is a good identification mark for machines coming toward one. For the rear view of a machine with the top up, the number and shape of the window panes in the back curtain are useful marks.
The purely logical points deserving emphasis in this familiar but tjrpical case are: first, the trustworthiness of the identification marks in spite of their triviality. The number and shape of the windows in the back curtain are just as positive and real as traits, that is, they are, logically regarded, just as important attributes of a particular class of machines as the number and shape of the cylinders; and second, the fact that using the marks in the way we do i3 purely descriptive, so far as concerns the recognition of an individual machine, but is defini- tive in so far as that machine is differentiated from any other kind of machine. Had there never been more than one automobile made, so that then there could be no question of distinguishing it from others of its kind, the windows would still be no less positive and real, though they would not, manifestly, then furnish distinguishing traits within the gen- eral class automobiles. But here there comes to view a difference of the utmost importance between the way attributes are definitive of man- made objects like automobiles, and natural living objects like men. In the first class of objects we are perfectly sure that many, usually most, of the attributes which the old logic would call accidents had no genuinely dependent relation to most of the other attributes of the object; while in living beings, especially of the higher classes, we are now certain that the great majority, if not all, the attributes, even those which formal logic would call accidents, are in vital relation with many, usually very many, other attributes. Thus recurring to the shapes of back curtain windows in automobiles and freckles on the nose of our hypothetical island mother, we know that the former have no fundamental relation to the more essential attributes of the machines, as, for example, the style of engine or carburetor or magneto ; while on the other hand we know with equal certainty that freckles are vitally related to, indeed are wholly dependent upon, various other attributes, notably the complex attribute known as complexion, which again is vitally related to the blood system, and so on.
There are few, if any, points at which biology is more at sea than
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