An enquiry concerning the principles of natural knowledge

by Alfred North Whitehead

and

are distinct event-particles, there are events separated from each other in which

and

respectively inhere.

Two events intersect if there are event-particles each inhering in both events; and conversely, there are event-particles inhering in both events if they intersect.

37.5 The fact that the instantaneous geometry within a moment is three-dimensional leads to the conclusion that the geometry for all event-particles will be four-dimensional. It is to be noted however that the straight lines for this four-dimensional geometry have so far only been defined for event-particles which are co-momental, namely the rects. Event-particles which are not co-momental will be called 'sequent.' Straight lines of the four-dimensional space joining sequent event-particles will be defined in [Chapter XI].