The conclusions reached in “First Principles” may be thus summed up:  over and over again in the five hundred pages devoted to their formulation, it is shown in various ways that the deepest truths we can reach are simply statements of the widest uniformities in our experiences of the relations of Matter, Motion, and Force; and that Matter, Motion, and Force are but symbols of the Unknown reality.  A Power of which the nature remains forever inconceivable, and to which no limits in Time and Space can be imagined, works in us certain effects.  These effects have certain likenesses of kind, the most general of which we class together under the names of Matter, Motion, and Force; and between these effects there are likenesses of connection, the most constant of which we class as laws of the highest certainty.  Analysis reduces these several kinds of effects to one kind of effect; and these several kinds of uniformity to one kind of uniformity.  The highest achievement of Science is the interpretation of all orders of phenomena as differently conditioned manifestations of this one kind of effect, under differently conditioned modes of this one kind of uniformity.  When science has done this, however, it has done nothing more than systematize our experiences, and has in no degree extended the limits of our experiences.  We can say no more than before whether the uniformities are as absolutely necessary as they have become to our thought relatively necessary.  The utmost possibility for us is an interpretation of the process of things, as it presents itself to our limited consciousness; but how this process is related to the actual process we are unable to conceive, much less to know.

Similarly we are admonished to remember that, while the connection between the phenomenal order and the ontological order is forever inscrutable, so is the connection between the conditioned forms of being and the unconditioned form of being forever inscrutable.  The interpretation of all phenomena in terms of Matter, Motion, and Force is nothing more than the reduction of our complex symbols of thought to the simplest symbols; and when the equation has been brought to its lowest terms, the symbols remain symbols still.  Hence the reasonings contained in “First Principles” afford no support to either of the antagonist hypotheses respecting the ultimate nature of things.  Their implications are no more materialistic than they are spiritualistic, and no more spiritualistic than they are materialistic.  The establishment of correlation and equivalence between the forces of the outer and the inner worlds serves to assimilate either to the other, according as we set out with one or the other.  He who rightly interprets the doctrine propounded in “First Principles” will see that neither the forces of the outer, nor the forces of the inner, world can be taken as ultimate.  He will see that, though the relation of subject and object renders necessary to us the antithetical conceptions of Spirit and Matter, the one is no less than the other to be regarded as but a sign of the Unknown Reality which underlies both.