What is a human? What is a self?

What makes humans not just matter?

I think this is the easiest of the two questions. It's our consciousness. At least, this is why humans have a certain kind of value that ordinary matter lacks. For instance, I can kick a rock, and this is neither good nor bad for the rock. However, if I kick you, this will probably be bad for you. So, what distinguishes humans from ordinary matter is that our lives can go well or badly. Put another way, we have interests. However, these interests are dependent on consciousness. If I found out that you were really a zombie (a being who is like a person in every respect except that they are not conscious), then I would not be harming you by kicking you, no matter how much you screamed. If you were a zombie, kicking you would be like kicking a rock. Note, though, that this argument applies to other conscious beings as well. So, a pig is not just matter in the same way that humans are not just matter. If you're looking for something that distinguishes all members of the species Homo sapiens from all other species and all other matter, my answer would have to be this: there is no such thing.

When do we become ourselves?

This is a hard question. It is a question about personal identity. You might say that we become ourselves whenever we gain consciousness. Unlike you, I think this probably happens before birth. But, since consciousness is a matter of degree, I don't think we are very conscious before birth, and not even that conscious immediately after birth. But I could be wrong about this; questions about what kinds of beings have consciousness and in what quantity are nutoriously difficult. In any case, I don't think consciousness is the criterion of personal identity. After all, do I die when I go to sleep? Is the person who wakes up in the bed the next morning a different person? If not, why not? You might say because I regain consciousness in the morning, I am still the same person. I only cease to be the same person when I lose consciousness forever. But this argument just presupposes personal identity. I could just as easily say that the consciousness of the person who wakes up in the morning is a new consciousness, but with all the same memories, desires, beliefs, etc. So consciousness by itself doesn't result in personal identity.

I think the most plausible conception of personal identity is this: we are the same person if we have an continuous, overlapping chain of memories, desires, beliefs, etc. So, a person can be understood metaphorically as a rope. No strand in the rope goes all the way from end to end, yet there is still one rope. Similarly, even if I lose all the memories I had when I was five, since there is a chain of memories leading from me at five to me now, I am the same person. However, this view also has its flaws. Consider this example from Derek Parfit's Reasons and Persons:

Scenario one: You enter the teletransporter. This is a machine that purports to transport you to Mars. It scans your brain and body, puts you to sleep, then destroys your brain and body. Next, it beams the information from the scan into space, which is then collected by a recieving unit on Mars. This recieving unit then reassembles your brain and body exactly as it was when you were scanned. You wake up with all the same desires, beliefs, memories, etc. Are you the same person? Most people will say answer Yes.

Scenario two: You enter the teletransporter. You are scanned. But, the machine fails to put you to sleep, and does not destroy your body. A man in a white coat explains that this is a new model. instead of destroying your body on Earth, it just sends a copy to Mars. However, there's been a slight malfunction. The you on Earth will have a heart attack and die with three or four days. But, the man reassures you that the you on Mars is perfectly healthy, and that you can be beamed back with no trouble. Do you feel reassured by this? Most people would answer No. They would not be reassured because the copy of them on Mars is not really them. But the only difference is that in this example, the destruction of you on Earth takes place a bit later. In both cases there is a continuum of memories, desires, beliefs, etc. But, in the latter case, our intuitions tell us that you on Earth and your copy on Mars are two distinct people. This undermines what I take to be the most plausible view of personal identity.

So, finally, here's what I think. I think there is no criterion of personal identity, because personal identity is an illusion. Technically speacking, when I talk about what I did yesterday, I am really talking about a person who existed yesterday with very similar desires, beliefs, memories, etc. But given the problems for personal identity such as the one above, I think we really have to deny that there really is an objective criterion of personal identity. In short, persons don't exist.

That's a really hard set of questions.

I can see that you've looked over many different philosophers and arguments.

To make this discussion solid lets throw in some reading for others.

Problem of identity see http://en.wikipedia.org/wiki/Ship_of_Theseus

Problem of Consciousness see http://en.wikipedia.org/wiki/Consciousness and http://en.wikipedia.org/wiki/Philosophy_of_mind

An answer would have to satisfy these hard questions and within the framework that you're alluding to. Which philosophical schools do we want to discuss?

Your a human.. Self is just what we call.. Ourselves?