chapter  5
20 Pages

## Relativity and the Problem of Space

It is characteristic of Newtonian physics that it has to ascribe independent and real existence to space and time as well as to matter, for in Newton’s law of motion the idea of acceleration appears. But in this theory, acceleration can only denote “acceleration with respect to space”. Newton’s space must thus be thought of as “at rest”, or at least as “unaccelerated”, in order that one can consider the acceleration, which appears in the law of motion, as being a magnitude with any meaning. Much the same holds with time, which of course likewise enters into the

with bodies; thus there is no space without bodies and hence no empty space. The weakness of this argument lies primarily in what follows. It is certainly true that the concept extension owes its origin to our experiences of laying out or bringing into contact solid bodies. But from this it cannot be concluded that the concept of extension may not be justiﬁed in cases which have not themselves given rise to the formation of this concept. Such an enlargement of concepts can be justiﬁed indirectly by its value for the comprehension of empirical results. The assertion that extension is conﬁned to bodies is therefore of itself certainly unfounded. We shall see later, however, that the general theory of relativity conﬁrms Descartes’ conception in a roundabout way. What brought Descartes to his remarkably attractive view was certainly the feeling that, without compelling necessity, one ought not to ascribe reality to a thing like space, which is not capable of being “directly experienced”.1