At the short of it, we all 'know' we exist (though, in reality, our existence might be of a far different nature from what we believe it is - as an example, we might be a giant computer simulation running on a gargantuan computer run by some other intelligence). And existence itself, even in physcis, is somewhat undefined! For instance, in quantum mechanics, we learn that we and the whole world are made up of interfering wave functions which cannot be directly shown to exist, and which can be expressed mathematically only with imaginary numbers. Think about that. We cannot directly show that wave functions (which make up everything) actually exist! Again, like Descartes, we assume we exist (though that existence, as in the computer simulation example), might be significantly different than what we suppose (a la the movie Matrix!). Now, assuming that we exist, you are proposing to make existence 'good.' Well, that's a moral axiom. And most moral systems include existence, at least to some degree, as a 'good.' Christianity does, though not as an absolute. But most moral systems have many other moral axioms as well. And truth in the next post!
Well, truth to me is that which exists. Which, one should note, does not necessarily preclude that which cannot be proven to exist - much truth may exist that we cannot prove to exist. We cannot currently prove that God exists - but we also cannot currently prove that wave functions (the basis of all reality, according to our physicist friends) exist. And we all know the emergence of existence conundra. - Did the universe (i.e., existence) form out of nothing, or out of something? And if out of something, how was that something created - and so forth. And as for moral truth - either that always existed (along with the existence of God?), or it was 'created' by someone simply positing a set of moral axioms that suit a lot of people. A third alternative is that such moral axioms were posited by outside intelligences - like aliens, and passed down to us. A fourth alternative is that God exists and that He posited those axioms. But what is interesting is that what distinguishes humans is not their ability to reason - but their ability to understand good and bad. There is some sort of resonance between our understanding of good and bad in our hearts, and the moral axioms that so many believe come from God. In actuality, most, when they look at humans, they see that many will make that resonance more important than even the will to survive or the will to benefit materially. That is why someone will risk their life to save a man in a buring car, or why someone will rush across a road to save a baby, or why someone will tell the truth when they don't have to, in order to help a stranger, etc. etc. In short, there seems to be a receptance in humans to things like the Christian moral code, even thoughh we are tempted frequently to ignore it. That's just a hint (among many, many) that there may be a preexsting, Godly moral code. The problem for those who don't believe in such is that you are left to posit your own moral axioms. ANd when you do, you must appeal to your own higher ideas of good and bad to select those which you think are 'good.' In short, therefore, either moral truth is preexistent, or we have lots of people running around (like you, or me, or Rand) making it all up. I find more indirect evidence for the former, and for obvious reasons, hope that I am right!