I also was puzzled by that sentence. The only thing I could think of was that he was saying that if the interaction among men was “random” (perhaps meaning only very occasionally and of limited significance as in passing each other at a distance in the woods) it would never occur to them to address how they should interact with each other ie the issue of rights. It is not that rights would not exist but rather that it would not need to be addressed in such a primitive state. It is only when their interactions became significant enough to impact their lives that it would occur them to establish rules about how they should act ie a social system. Make any sense?
