These event-particles are the various situations of the material particle.

We usually express this fact by adopting our natural space-time system and by talking of the path in space of the material particle as it exists at successive instants of time.
We have to ask ourselves what are the laws of nature which lead the material particle to adopt just this path among event-particles and no other.

Think of the path as a whole.

What characteristic has that path got which would not be shared by any other slightly varied path?
We are asking for more than a law of gravity.

We want laws of motion and a general idea of the way to formulate the effects of physical forces.
In order to answer our question we put the idea of the attracting masses in the background and concentrate attention on the field of activity of the events in the neighbourhood of the path.