In what sense is being put to death a punishment? How we can talk about things like "suffering" or "loss" if a person is dead (i.e., not conscious)?

Most of Thomas' response focuses on your observation that once one's dead one's "not conscious", and he nicely tries to clear a space for the possibility of harm's being done to someone even if that person doesn't feel the harm. But in most of the cases he considers, there is still someone to be the subject of the misfortune: the clueless entrepreneur, for instance, is still around to have his interests set back (even if he's not aware that that is happening). Death is rather peculiar, however, in that it's a misfortune that eliminates from the world the subject of the misfortune. (Of course, someone's death might be a misfortune for others. But as you note, we put people to death to punish the very people who, if the punishment is carried out, are no longer around.) Once one's dead, not only does one cease to experience things but one ceases to have interests too. That's what makes your question hard. It's really the question the Ancients (and everyone else) argued about: whether one's own death...

Is this a probable way to think about death?: the same "nothingness" we 'experience' before we are born and have memory is what we will 'experience' when we die. (It just makes sense to me - what about to whomever reads this?)

I agree with you that the state before you're born is like the state after you've died in that in neither will you exist. But I don't agree that these are states that we somehow experience. I note that you yourself place "experience" in scare quotes, indicating that perhaps it's not to be taken literally. And that's right: the period after you've died and before you're born is not a period in which you are around and having, how can we put it?, rather bland experiences. No. Before you're born and after you've died, there is no you to be the subject of any experience. Your birth brings that subject of possible experiences into being and your death terminates its being.

Why don't people who say that when you die you go to a better place kill themselves? If death is a better place, why are they staying in this "lesser" world? Is it that they are unsure if they are right or not and don't want to risk it? -Dylan (13)

Maybe some people are, as you say, confident but still not certain about the afterlife. Perhaps some don't wish to cause pain to their friends or loved ones, who will miss them terribly. And perhaps some don't believe that they have the right to "quit their station in life" (as the philosopher John Locke put it): they are God's property and have no right to destroy themselves.

I believe that death is nothingness, when my conscious mind is dead, nothing else will exist. What are your thoughts on this and are there any writings on this theory?

Are you saying that you believe that when you die, you will be utterlygone and not survive in any way? Or do you mean that when you die,everything will cease to exist? The first thought is one that many areinclined to, especially if they do not accept a religion that promisesan afterlife. The second thought is far less common. I suppose that ifyou were a solipsist , someone who believes that only he exists, then you might come to the conclusion that your death spells the end of everything. You can find an on-line introduction to solipsism here .

If someone murders many people, is it fair that they die once for their multiple victims?

I'm not sure that fairness enters into it. Whom would one be treating unfairly by condemning a murderer to just one death? His victims? Once dead, they are not being treated in any way at all; so they're not being treated unfairly relative to the murderer. Perhaps you mean that it would not be right or just for the murderer to die just once. But even if we could kill someone more than once (which we can't), why does justice demand that someone be made the victim of precisely the crime he or she committed against another? If you think of all the crimes people commit against one another, do you find that nothing short of visiting the same wrong against the perpetrator will right the moral balance?

Is it possible for one to possibly know what exists after death? As humans, with a mind that exists solely as physical matter (and a soul, if religion is counted), when we die, how is it possible for this purely physical mind to keep on functioning, and allow us to realize that we are dead? As well, if we have souls, how can an entity created purely of energy (or whatever you think a soul is made of) have senses and detect that it exists, or even think?

If you believe your death spells your total annihilation then your death presents more than a problem of how to acquire knowledge: once you die, there will be no you around to know (or not to know) anything. Indeed, there won't be a you around to undergo non-existence so there won't be anything (for anyone) to know. Non-existence isn't a particular kind of state that presents challenges to our knowledge; your non-existence entails that you are no longer around to be in any state. If you think death is merely the end of your corporeal existence and that your soul survives, then I'm not sure what to say: for, like you, I don't know what souls are or how they acquire knowledge.