Moreover, the particular water with which the experimenter actually deals never, as matter of fact, shows itself twice; it never recurs. It has just as much exclusive uniqueness as is possessed by the career of Julius Caesar or Abraham Lincoln. That particular portion of water could never have presented itself at any other portion of the world's history, any more than the life of one of the individuals named could have been lived in exactly the same way at any other epoch. To deny this is simply to fall into the error of the mediæval realist whom the average scientist is so fond of ridiculing. It is to admit the existence of some generic water which is no water in particular, and yet all waters in general.
Yet, you say, there is a difference. Certainly; but it is a difference of interest, or purpose, not of existence, physical or metaphysical. Julius Caesar served a purpose which no other individual, at any other time, could have served. There is a peculiar flavor of human meaning and accomplishment about him which has no substitute or equivalent. Not so with water. While each portion is absolutely unique in its occurrence, yet one lot will serve our intellectual or practical needs just as well as any other. We can have substitution without loss. Water from the nearest faucet may slake thirst as well as that from the Pierian spring. And what is of more importance to our immediate problem, any one case serves just as well as any other to demonstrate that which is of scientific interest: the process by which water is made, and by which a great body of other and quite dissimilar substances are called into being. We do not care scientifically for the historical genesis of this portion of water: while we care greatly for the insight secured through the particular case into the process of making any and every portion of water. It is this knowledge of process of generation that constitutes the controlled interpretation which is the aim of science.
Hence our final scientific statement assumes the generalized form we are familiar with in physical science, instead of the individualized form we demand of historical science. Hence also the apparent disruption and dislocation from context in the stream of serial reality. The modern logician has correctly apprehended
