So far, then, the deductions of science are found to be in striking harmony with the teaching of revelation--the existing order of the universe had a beginning; the forms, relations, laws, harmonies of the Cosmos had a commencement in time. We may now proceed to the consideration of the second question: Had that which is the _ground_ of all form, the _subject_ of all changes and relations, a beginning? Had the _matter_ of the universe a beginning? That we may fairly present the answer which modern science offers to this question, we must premise, in general, that it confesses its inability, in the present stage of physical knowledge, to determine what is the ultimate or internal constitution of matter. Many scientists of to-day are of the opinion expressed by Grove[168] that "probably man will never know the ultimate structure of matter." Others, as, for example, Thomson, Bayma, McVicar, and Challis, entertain the opinion that physical science is competent to discover all the minutiæ of molecular actions, and when this has been achieved, the question as to the ultimate constitution of matter can be finally determined. There is one guiding principle, recognized alike by the physicist and the metaphysician, namely, that substances, ultimate entities, are known, and can only be known in and through their respective phenomena. An exact enumeration and careful colligation of all the phenomena are therefore indispensable prerequisites to the solution of the problem. Meantime nothing is more remarkable, even in the present state of physical science, than the fact that, under the subtile analysis of modern physics, much that we have been accustomed to regard as phenomena of matter dissolves and disappears, surviving only as phenomena of _Force_. The phenomena of heat, light, color, sound, electricity, and magnetism are now "modes of motion"--manifestations of one and the same omnipresent energy, which is transferred from one portion of matter to another, and modified or transformed simply by the mechanical arrangements and collocations of matter. The opinion is rapidly gaining ground that even chemical action is a mode of motion, and Professor Norton does not hesitate in affirming that "_all the phenomena of material nature result from the action of force upon matter_."[169] All that we mean by a Material Force "is a force which acts _upon_ matter, and produces in matter its own appropriate effects."[170] It is not an attribute of matter, not a quality inherent in matter, but a mode or state superimposed upon matter.