universals and humanness

Assuming that I am human, and my peers are human as well, then it follows that we share something in common. We all seem to share in common the property (humanness), just as a lemon would share the property yellowness with another lemon. But let us look closer at the relationship between lemons for a second. Provided of course that the lemons in question are good and ripe they will have said commonality. So then, …

…But that still doesn't make sense because a universal being a universal is not something physical, whereas the hand is something physical. So how did the physical molecules act upon a nonphysical thing? (Anyone remember the mind-body problem?) However, this is about the only real problem I can think of; there's no vicious regress at work in this notion. That being the case, I find it far more convincing that universals are Aristotelian in nature.