From my answer to the question, Why would a good God allow suffering to exist?
The fact that God Himself died on the Cross - the most atrociously painful conceivable way to kill anyone - strongly suggests that there is something about pain and evil that God could not avoid or forbid, at least not without nullifying His relationships with us. God, we know, can do anything except the absurd, and it seems to me likely that a creation without physical pain would be absurd. Pain, after all, is first of all a danger signal, a warning that the physical and mental integrity of a conscious living being is under threat. Can we conceive of a world with no threat of any kind? I don't think I can.
What is more, it is not altogether clear that all living beings feel it. I am no scientist, but I understand that where no central nervous system exists, reactions against pain are not observed. Plants don't show any reaction to being cut or chopped down. And in fact, I would go further and say that pain only gains a moral significance - the reason why we react with horror to it in the first place - in so far as the beings who suffer it and those who inflict it are capable of thought and feeling. Nobody blames a female praying mantis for devouring her mate during copulation, not even her mate - after all, they have carried on with what is to us a horrible way to reproduce for millions of years.
Blame begins when a child inflicts pain on an insect, because, even though the insect is probably incapable of thought and feeling, the child is, and ought to know that the insect is feeling that same thing that he himself, the child, hates to feel when it strikes him. And blame and anger reach the height when it is a man inflicting pain on another man, because in our case the moral dimension is there in its fullness. In other words, the problem of pain, as a moral problem, is only one side of the problem of evil; and at that point you have to ask whether God could forbid moral evil in creation without depriving us of free will, which would have made us wholly unlike him and our own creation no better than setting up a puppet theatre.
What is more, it is not altogether clear that all living beings feel it. I am no scientist, but I understand that where no central nervous system exists, reactions against pain are not observed. Plants don't show any reaction to being cut or chopped down. And in fact, I would go further and say that pain only gains a moral significance - the reason why we react with horror to it in the first place - in so far as the beings who suffer it and those who inflict it are capable of thought and feeling. Nobody blames a female praying mantis for devouring her mate during copulation, not even her mate - after all, they have carried on with what is to us a horrible way to reproduce for millions of years.
Blame begins when a child inflicts pain on an insect, because, even though the insect is probably incapable of thought and feeling, the child is, and ought to know that the insect is feeling that same thing that he himself, the child, hates to feel when it strikes him. And blame and anger reach the height when it is a man inflicting pain on another man, because in our case the moral dimension is there in its fullness. In other words, the problem of pain, as a moral problem, is only one side of the problem of evil; and at that point you have to ask whether God could forbid moral evil in creation without depriving us of free will, which would have made us wholly unlike him and our own creation no better than setting up a puppet theatre.