PLACE OF HYPOTHESIS IN EXPERIMENTAL SCIENCE. 557 patience in making the observations and ingenuity in con- triving the experiments necessary to test the theory, are alike indispensable to scientific progress. I have said that science does not rest content with explaining phenomena in terms of events. This is especially true of modern science, which is chiefly distinguished from ancient science by the prominence given to the idea of force. Phenomena having been explained in terms of insensible motion, molar and molecular, these latter are in their turn explained in terms of force. Dynamism would be more appropriate than Materialism as a designation of the modern scientific movement, the idea of inertia having given place to that of an equilibrium of forces. Of force the empirical logic knows not what to make : it is difficult to extract from its exponents any con- sistent doctrine on the subject. As, however, Mill illus- trates his chapter on the composition of causes by examples of the composition of forces, it is safe to assume that he at least regarded force as synonymous with cause, and there- fore reducible to uniformity of antecedence. This view, however, is radically unscientific. Science does not regard force as anteceding its results at all : it regards them as strictly synchronous. Gravitation, cohesion, chemical affi- nity, do not antecede the various phenomena which they condition, but are exhibited in them. The force of which Mr. Spencer writes with such impressiveness is neither an event nor any number of events, but the condition of all events happening. The conception is indispensable to science, which, as I have said, cannot rest in mere events ; but it is not empirically verifiable. Even if we take the step which Mr. Spencer declines to take, and identify physi- cal forces with that force which we know immediately as exerted by ourselves in volition, still the projection of such force into the universe at large remains a mere analogy wholly " unsusceptible of being ultimately brought to the test of actual induction ". If the foregoing account of causation and scientific method is true, a law of causation will be definable as an hypothesis by which several events or sequences of events are deduced from one and the same cause or combination of causes. As such it will be a relation not of sequence, but of coexistence and community. There will thus be no radical distinction between cause and law ; rather every cause so soon as defined will be itself a law, provided only the phenomena are deducible from it. A law, in fact, is simply the definition of a given cause. This point is so clear that illustration
