But what we actually perceive is an approximation to the instantaneous space indicated by event-particles which lie within some moment of the time-system associated with our awareness.

The points of such an instantaneous space are event-particles and the straight lines are rects.

Let the time-system be named {alpha}, and let the moment of time-system {alpha} to which our quick perception of nature approximates be called M.Any straight line r in space {alpha} is a locus of points and each point is a point-track which is a locus of event-particles.

Thus in the four-dimensional geometry of all event-particles there is a two-dimensional locus which is the locus of all event-particles on points lying on the straight line r.

I will call this locus of event-particles the matrix of the straight line r.