De Motu (Berkeley's Essay) - Motion in Space

Motion in Space

Absolute space contains no bodies. But, as such, it would not be observable. Nothing is denoted by the words "absolute space." Motion and space are relative. They presuppose a relationship to some other body through which they are determined. For a wider view, it would be useful to consider motion relative to the fixed stars, which would be considered as being at rest, instead of to absolute space. Just as we cannot know absolute space, we cannot know whether the whole universe is at rest or is moving uniformly in a direction.

To determine the true nature of motion, we must follow three rules: (1) distinguish mathematical hypotheses from the nature of things; (2) beware of abstractions; (3) consider motion as sensible or imaginable and be content with relative measures.