It's hard to prove that they aren't mere coincidence. It very well could be. However, since i believe that there is an infinite intelligence and we are part of it... i would say synchronicity's happen bc we tap into that infinite intelligence. Think of an A.I. in the future so advanced that it could think of every possible chess move that there is. Furthermore, this A.I. knows every chess move against anyone you put it against. That still doesn't scratch the surface of an infinite intelligence ("source"). This source would not only know every possible chess move, it would know any possible in any world, it would know every chess move you and everyone could and will make, it knows everything. Therefore, the future doesn't have to play out in order for this source to know what will happen. You come from this source, therefore, if you can momentarily tap into it... you will also know what is about to happen. I believe your higher self is still in source state. Synchronicity's are just one way it guides you through this experience.