Now the scientific method is a method of getting knowledge by inference, and that of two different kinds. One kind of inference is that which is used in the physical and natural sciences, and it enables us to go from known phenomena to unknown phenomena. Because a stone is heavy in the morning, I infer that it will be heavy in the afternoon; and I infer this by assuming a certain uniformity of nature. The sort of uniformity that I assume depends upon the extent of my scientific education; the rules of inference become more and more definite as we go on. At first I might assume that all things are always alike; this would not be true, but it has to be assumed in a vague way, in order that a thing may have the same name at different times. Afterward I get the more definite belief that certain particular qualities, like weight, have nothing to do with the time of day; and subsequently I find that weight has nothing to do with the shape of the stone, but only with the quantity of it. The uniformity which we assume, then, is not that vague one that we started with, but a chastened and corrected uniformity. I might go on to suppose, for example, that the weight of the stone had nothing to do with the place where it was; and a great deal might be said for this supposition. It would, however, have to be corrected when it was found that the weight varies slightly in different latitudes. On the other hand, I should find that this variation was just the same for my stone as for a piece of iron or wood; that it had nothing to do with the kind of matter. And so I might be led to the conclusion that all matter is heavy, and that the weight of it depends only on its quantity and its position relative to the earth. You see here that I go on arriving at conclusions always of this form; that some one circumstance or quality has nothing to do with some other circumstance or quality. I begin by assuming that it is independent of everything; I end by finding that it is independent of some definite things. That is, I begin by assuming a vague uniformity. I always use this assumption to infer from some one fact a great number of other facts; but as my education proceeds, I get to know what sort of things may be inferred and what may not. An observer of scientific mind takes note of just those things from which inferences may be drawn, and passes by the rest. If an astronomer, observing the sun, were to record the fact that at the moment when a sun-spot began to shrink there was a rap at his front door, we should know that he was not up to his work. But if he records that sun-spots are thickest every eleven years, and that this is also the period of extra cloudiness in Jupiter, the observation may or may not be confirmed, and it may or may not lead to inferences of importance; but still it is the kind of thing from which inferences may be drawn. There is always a certain instinct among instructed people which tells them in this way what kinds of inferences may be