If we say that science is organised knowledge, we are met by the truth that all knowledge is organised in a greater or less degree—­that the commonest actions of the household and the field presuppose facts colligated, inferences drawn, results expected; and that the general success of these actions proves the data by which they were guided to have been correctly put together.  If, again, we say that science is prevision—­is a seeing beforehand—­is a knowing in what times, places, combinations, or sequences, specified phenomena will be found; we are yet obliged to confess that the definition includes much that is utterly foreign to science in its ordinary acceptation.  For example, a child’s knowledge of an apple.  This, as far as it goes, consists in previsions.  When a child sees a certain form and colours, it knows that if it puts out its hand it will have certain impressions of resistance, and roundness, and smoothness; and if it bites, a certain taste.  And manifestly its general acquaintance with surrounding objects is of like nature—­is made up of facts concerning them, so grouped as that any part of a group being perceived, the existence of the other facts included in it is foreseen.

If, once more, we say that science is exact prevision, we still fail to establish the supposed difference.  Not only do we find that much of what we call science is not exact, and that some of it, as physiology, can never become exact; but we find further, that many of the previsions constituting the common stock alike of wise and ignorant, are exact.  That an unsupported body will fall; that a lighted candle will go out when immersed in water; that ice will melt when thrown on the fire—­these, and many like predictions relating to the familiar properties of things have as high a degree of accuracy as predictions are capable of.  It is true that the results predicated are of a very general character; but it is none the less true that they are rigorously correct as far as they go:  and this is all that is requisite to fulfil the definition.  There is perfect accordance between the anticipated phenomena and the actual ones; and no more than this can be said of the highest achievements of the sciences specially characterised as exact.

Seeing thus that the assumed distinction between scientific knowledge and common knowledge is not logically justifiable; and yet feeling, as we must, that however impossible it may be to draw a line between them, the two are not practically identical; there arises the question—­What is the relationship that exists between them?  A partial answer to this question may be drawn from the illustrations just given.  On reconsidering them, it will be observed that those portions of ordinary knowledge which are identical in character with scientific knowledge, comprehend only such combinations of phenomena as are directly cognisable by the senses, and are of simple, invariable nature.  That the smoke