The question below consists of a set of labelled sentences. Out of the four options given, select the most logical order of the sentences to form a coherent paragraph.

P- And if I think about something which didn't happen I start thinking about all the other things which didn't happen.
Q- But there is only ever one thing which happened at a particular time and a particular place.
R- And there are an infinite number of things which didn't happen at that time and that place.
S- A lie is when you say something happened which didn't happen.