Know your probabilities in cities [small spoilers]
So why did Jean-Louis started looking at the probability theorem in a sudden burst as if he wanted to crack down a secret code which city holds. Of course, he wanted to see his blond sweetie again and wanted to calculate his next seeing with his engineering mind.This is not a metaphysical engineering quest. There are some spots in the movie which is more supportive this theorem.
Vidal and Françoise known each other. This is more than a mere knowing, it seems they had something intimate between before. An affair maybe which let Françoise to meet Maud's ex-husband,whom will be her next lover, by Vidals connection with Maud. Or maybe after Françoise split with Maud's ex-husband, she meet Vidal by knowing Maud. Or shes just saying truth about its small university and seeing teacher is very common. However i would ask, "what was that look on her face when she met Vidal?" Some guilt, some embarrassment or shame…
So the Vidal-Françoise-Maud-Maud's Ex had a quite interesting relation in a small town where circumstances let them meet each other.
Jean-Louis was really after something, there is a real probability of meeting someone which might well connected with our past or future in another way.