John Stuart Mill was a childhood prodigy, as you say, but in later adolescence he suffered a "nervous breakdown" (probably depression) which he thought was caused by too much intellectual work as a child. So, at the same age you are now, he was not very functional. He also died when he was 67--not a long life by today's measures. There are many routes to academic accomplishments; perhaps hard work is the only thing they have in common, and you know that you are capable of that. In any case, you cannot change the past or guarantee the future--only work with the present. If you enjoy academics and aspire to greatness, I wish you the best of luck!
Hi, Miriam. I completely agree. The concept of illness is very flimsy. It is something like: an abnormality or disorder of a mental or physiological organ or system. Attempts to give a serious scientific account of 'normal' or 'orderly' have proved unsuccessful. Illness is just a vague folk notion and probably does not correspond to anything more scientifically or philosophically solid. Questions about the true underlying nature of specific mental illnesses (psychiatric disorders as they are now called), their treatment etc. are best deal with case by case. The same applies to physical illnesses though. There is nothing special about physiology here.
You ask an interesting question about the process of evolution. Neo-Darwinians typically argue that species evolve by natural selection on random mutations. At any particular time, there is more than one kind of random mutation that is of selective advantage, and it is contingent which one of these (if any) occurs. So evolutionary history has a certain randomness and unrepeatability. If we recreated Neandertals and did not interbreed with them, they might evolve into yet another (new) human subspecies.
Some biologists have argued that some mutations are directed--i.e. not random and in response to specific environmental challenges. To the degree that this is so (and that environmental challenges repeat themselves) evolution might repeat itself. But this is a controversial theory and is not generally thought to account for much mutation.
Actually the universe is not infinite, although it is extremely large. Your claim that "it is inevitable that at least one of the millions of planets has the required characteristic for life" is not a logical claim (it is not true because it follows the laws of logic); it is an empirical claim and depends crucially on the likelihood of (a) a suitable planet and (b) suitable evolution on that planet. We don't yet know how likely or unlikely the evolution of life is, because our understanding of evolution, and life, is paltry. Intelligent design theorists take advantage of this ignorance to argue that a designer was necessary for the wonderful yet highly improbable complexity of life. But in fact we do not know how (un)likely life is in this universe or how a designer might work in the universe.
I think you are right to discern that the "playing God" objection to stem cell research/cloning is not what it seems to be. Those who offer this objection seem quite comfortable with the idea of "playing God" in well proven medical interventions e.g. appendectomy for appendicitis, C-section for obstructed labor, chemotherapy for leukemia. Of course there are some people (Christian Scientists, for example) who forgo most medical care on religious grounds. But the vast majority of those who worry about "playing God" with stem cell research/cloning are happy consumers of the best that health care has to offer. The question is, why don't they extend that happy consumer attitude to stem cell research/cloning? I am not sure of the answer to this, but I think it may have to do with the uncertainty that currently exists around these new technologies (will they work? will they produce monsters of some kind?). So it may be a risk aversive attitude of the kind "leave it to God, we don't know enough to intervene in this area." It expresses caution about experimenting with human beings, and modesty about our technological abilities, which is appropriate (if not taken too far).
Of course for every person who says that we shouldn't "play God" there is usually another person who says "God helps those who help themselves." Religious language can be used on both sides of this debate.
Your last sentence is correct, I think, with the exception of the word "improve," which I would replace with "modify" or "enhance." "Improvement" raises all the questions that critics of eugenics have raised about classifying human beings into better or worse.
By the way, we are already Transhumans, if you count glasses, sneakers, computers, etc. Perhaps the movement Transhumanism want the modifications integrated with our biology. But why would that be better?