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will rernain as the irrefutable basis for all subsequent philosophic thought.

Another item in the common-sense doctrine concerns empty space and locomotion. In the first place, the transmission of light and sound shows that space apparently empty is the theatre of activities which we do not directly perceive. This conclusion was explained by the supposition of types of subtle matter, namely, the ether, which we cannot directly perceive. In the second place, this conclusion, and the obvious behaviour of gross ordinary matter, show us that the motions of matter are in some way conditioned by the spatial relations of material bodies to each other. It was here that Newton supplied the great synthesis npon which science was based for more than two centuries. Newton’s laws of motion provided a skeleton framewotk within which more particular laws for the interconnection of bodily motions could be inserted. He also