It is a well known fact that the beginning of analytic philosophy is grounded in Moore's and Russell's rebellion against the idealism of 19 century England. Despite of Russell's sharp criticism of his own idealistic phase, some important theses of his later realistic philosophy can only be understood in the context of a critical discussion of his own earlier idealistic philosophy. In this paper I will analyse the concept of the . This is the central logical and philosophical concepts of Russell's only philosophically relevant book of that time. According to Russell, both time and space are the fundamental forms of externality of our world. I will analyse and criticise his arguments in support of this claim. I will end the paper by showing that Russell's theory of relations – one of his most important legacies to analytic philosophy – arises out of his work on the foundations of geometry.