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Recently I was watching the famous "Powers of Ten" video which starts with a couple at a picnic and moves out to the far edges of the universe, moving ten times further out each second. After this the camera goes back to the couple and enters the hand of the man at the picnic, moving through layers of skin, blood cells, molecules, atoms and finally a haze of interacting subatomic particles. What struck me about this part of the video is that if the camera was to move beyond the boundaries of the man's hand we wouldn't be able to tell. There is no demarcation between the subatomic particles which make up the man's hand and the subatomic particles which make up the surrounding air. So, in what sense do seperate entities exist? Is seperateness an illusion inherent to the experience of beings at a macroscopic scale, similar to our illusion that objects are "solid" when in reality an atom is comprised mostly of empty space?

I love that video! Thank you for your excellent question. Of course, you are correct in saying that there is no sharp demarcation between the hand and its air around it. A water molecule that is part of the hand may at some point evaporate into the surrounding air. There is no particular moment at which the molecule leaves the hand and becomes part of the atmosphere. Its chemical bonds to other "hand" molecules weaken gradually, its distances from those molecules increase gradually, and even if these quantities do not change continuously (in the mathematical sense), there is no magic bond strength or distance at which the molecule officially leaves the hand and joins the air. That being said, the fact that there is no sharp distinction does not guarantee that there is no distinction at all -- that "separateness is an illusion inherent to the experience of beings at a macroscopic scale". After all, there is no sharp distinction between night and day -- yet night is not the same as day. It...

How do we know our right hand from our left hand when there is literally nothing that can be said about one which cannot be said about the other? -ace

That is a great question! Of course, all of the relations among the parts of my right hand are the same as the relations among the parts of my left hand. (We might have to imagine slightly idealized hands here, since someone might happen to have a cut on their right hand but not on their left.) But there are relations to external things that differ between your right and left hands. For instance, my left hand is currently nearer to the "a" key on my typewriter than my right hand is. Because my hands can stand in different relations to other things, I can learn which is "right" and which is "left". For example, my mother presumably held my right hand and not my left when she said "That's your right hand, Marc." In this way, I learned which of my hands was "right". However, let's turn from the question of how we know which hand is right and which is left (an epistemological question -- a question about knowledge) and ask a metaphysical question (a question about reality). Suppose there were a...

A couple of years ago I read an article about an experiment where the genes of a jellyfish were spliced into a rabbit - the result: a rabbit that glowed in the dark. My question is, science aside, is this a rabbit?

Good question. I'm not sure that there's any answer "science aside", since the notion of being a member of a given biological species (in this case, some sort of rabbit) is a scientific concept. It is up to science to tell us what species are, whether there are any such things, why they arise and go extinct, and so forth. One popular conception of a biological species is that a species is a group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. In other words, members of the same species form a united gene pool, so that a beneficial adaptation appearing in that pool could spread throughout it, whereas barriers prevent its spreading outside of the species. On this view, which is obviously motivated by evolutionary considerations, the mere fact that the creature you have mentioned differs from all (other) rabbits in possessing certain genes that allow it to glow in the dark does not rule out the possibility that it is a...