The ontology of the Tractatus is spatial. The existence and nature of space are deduced a priori, and it is therefore called "logical space". The argument that follows is that logical space, in itself and in relation to time and change, shares fundamental features with the space postulated by modern science,¹ and that modern science is a particular form of description of logical space. This connection is the first and the essential indication that the class="EmphasisTypeItalic ">Tractatus philosophy belongs squarely within the modern tradition.