A thorough examination of these two conceptions of nature will show that they involve two very different hypotheses as to the relations between laws and the facts which they govern. As he looks higher and higher, the believer in dynamism thinks that he perceives facts which more and more elude the grasp of laws: he thus sets up the fact as the absolute reality, and the law as the more or less symbolical expression of this reality. Mechanism, on the contrary, discovers within the particular fact a certain number of laws of which the fact is thus made to be the meeting point, and nothing else: on this hypothesis it is the law which becomes the genuine reality. Now, if it is asked why the one party assigns a higher reality to the fact and the other to the law, it will be found that mechanism and dynamism take the word _simplicity_ in two very different senses. For the first, any principle is simple of which the effects can be foreseen and even calculated: thus, by the very definition, the notion of inertia becomes simpler than that of freedom, the homogeneous simpler than the heterogeneous, the abstract simpler than the concrete. But dynamism is not anxious so much to arrange the notions in the most convenient order as to find out their real relationship: often, in fact, the so-called simple notion--that which the believer in mechanism regards as primitive--has been obtained by the blending together of several richer notions which seem to be derived from it, and which have more or less neutralized one another in this very process of blending, just as darkness may be produced by the interference of two lights. Regarded from this new point of view, the idea of spontaneity is indisputably simpler than that of inertia, since the second can be understood and defined only by means of the first, while the first is self-sufficient. For each of us has the immediate knowledge (be it thought true or fallacious) of his free spontaneity, without the notion of inertia having anything to do with this knowledge. But, if we wish to define the inertia of matter, we must say that it cannot move or stop of its own accord, that every body perseveres in the state of rest or motion so long as it is not acted upon by any force: and in both cases we are unavoidably carried back to the idea of activity. It is therefore natural that, _a priori,_ we should reach two opposite conceptions of human activity, according to the way in which we understand the relation between the concrete and the abstract, the simple and the complex, facts and laws. [Sidenote: Determinism: (1) physical (2) psychological. Former reducible to latter, which itself rests on inaccurate conception of multiplicity of conscious states or duration.]