There are several movies which play with the concept of people’s paths crossing and the consequence of such interactions. It’s funny these movies are almost automatically so popular solely through this premise, because people’s paths cross all the time. We influence each other’s lives all the time.

The more complex an agent (or its relationship with us), the more its capacity to influence us — one hour of interaction with a toy will shape us less than the same hour spent interacting with our friend, which in turn will shape us less than one hour of interacting with a parent. However (what is much more interesting than the obvious crossing of the paths depicted in those movies, maybe with the exception of Run Lola Run) our fortunes are chaotic: small perturbation in the inputs may alter our life significantly. This means that all sorts of paths cross in a way that we’re probably not particularly aware of. If we cut someone off on the road, we’ve influenced them — usually in a negative way (by causing them to become angry). When we go to the mall, or in general walk around, our gaze briefly catches the expression of each of the people we pass. It’s a subtle kind of interaction, but it’s possible that they yield tremendous difference in our lives.

A friend of mine had an interesting idea — given that our paths cross all the time, we are embedded (to various extents and with various accuracy) in the memories of many people, even if it’s just a few photons that reach a child’s eye as he gazes down the window of an airplane passing thousands of feet above me camping in a National Park with my friends. This collective memory connects us all — and creates a sense of continuity. He suggested that our identity could simply be the sum of all these impressions. Moreover, if we could tap into this collective memory, we could travel in time and space — experiencing events as people before us experienced them, and those people before them, etc.