This chapter concerns the reformulation of the traditional galilean conception of the world required by Einstein's theories of special and general relativity, and the significance of that reformulation for the truth of basic contents and for the plausible realization of our causal experience. Section 1 is a brief exposition of some crucial features of special and general relativity.¹ Section 4 applies those considerations to the two issues which immediately concern us. Sections 2 and 3 provide a bridging discussion. They concern the concrete significance, the proper interpretation, of relativity, and relativity's explanation of the galilean appearance of the world.