The distinction between the individual and the statistical aspect of a problem may be further illustrated in the much-discussed question of the differences in brain characteristics of men and women. When the claimants for woman's equality point to the acknowledged inability of an anatomist to determine whether a particular brain belonged to a man or a woman as conclusive evidence of their contention, they unconsciously assume that the problem is capable of determination in the individual specimen. A sounder logic would insure greater caution. The differences in question may be certainly established and typical, and yet depend upon statistical, not upon individual data. Give the anatomist a goodly number of fairly selected brains and tell him that all the women's brains are in one group, and all the men's brains in another, and he will tell you which group is feminine, which masculine; and this more than offsets his failure in the former test. It establishes a statistical regularity. Individually we may argue that many women of our acquaintance have larger heads than the men; that the English, are not taller than the French, because the Frenchmen we have chanced to meet have been quite as tall as the Englishmen of our acquaintance; that the laws of chance do not apply to the gaming-table, because on that basis we should have come out even and not as losers; and that coincidences cannot explain our strange mental experiences, because they are altogether too peculiar and too frequent. It is only in the most complete stages and in the more definite realms that knowledge becomes applicable accurately and definitely to individual cases. For the present it is well if, with such abstruse or rather indefinite material, we can glimpse the statistical regularity of the entire group of phenomena, trace here and there the possible or probable application of general principles, and refuse to allow our opinions to be disarranged by rather startling individual cases. The explanation of these, however interesting they may be to ourselves or entertaining to others, is not the test of our knowledge of the subject.
I pick up a stone, and with a peculiar turn of the hand throw it from me; probably no student of mechanics can exactly calculate the course of that projectile,--nor is it worth while. What he can do is to show what laws are obeyed by ideal projectiles, ideally thrown under ideal conditions, and how far the more important practical cases tend to agree with or diverge from these conditions. It is unfair to test his science by its minute applicability to our special experiences.