The only way to attain absolute truth is to be God. We are not God therefore we cannot attain it. However, it does exist. It's just that we, as humans, are imperfect and cannot achieve that level of superiority. That is solely up to God to have and we cannot ever attain it.
I think that absolute truth's existence is necessary for any type of intelligible, well, anything. The very fact that this site and this question make sense prove the existence of absolute truth. I would be forced to ask the question of those who respond no, is it absolutely true that there is no absolute truth?
Furthermore, I believe that the existence of absolute truth begs the question....What standard of truth is there? I think answering that question ultimately leads back to God.
Think about it. In areas other than morality we do not consider truth to be relative. Would you take somebody else's prescription because the truth that such a thing is harmful is somehow relative?
In fact, everything in this universe is absolute. Even humans are absolute and predictable in behavior. Therefore, surely there is such thing as absolute truth pertaining to morality.
To keep this short and sweet, any claim that there is no such thing as absolute truth, or that achieving absolute truth is itself a truth claim. To say that "Absolute truth does not exist" you are claiming that you know the truth about the matter. Of course there's absolute truth!
By simple logic, absolute truth must exist. Since there is existence in our universe (and probably beyond), there must also be an absolute truth to it. And if there was no existence at all, then the truth would be, that nothing exists. So either way, there is an absolute truth.
Nothing can truly be proven because everything we know is based on perception. Gravity is an idea that is perceived to work 99.999999% of the time, but you can't be sure that it will work every time because you haven't tested it infinitely. Moreover, gravity might theoretically be caused by something else entirely, something that effects the world in the exact same way, and we wouldn't be able to tell. Yoda could be at the center of the earth, which, for all that truth knows, could be a black hole and an iguana at the same time, and he could be using his force powers to pull all matter towards all matter. Each individual's truth is based on their perception of reality, and even though the sky might be blue in reality, each individual's perception of the color might be different and we wouldn't know. That is to say, truth exists and we should forever strive to find it, but we will never actually be sure of its true identity because our perception of it is but a mirror image viewed in a looking glass whose uniformity cannot be assured.
Since absolute truth implies that there is one unalterable and permanent fact that fits everyone. This assumption can is invalid if we look at each individual person or being. What is true to one person might not necessarily be true to everyone else. For example, a Christian would believe in his "absolute truth" and a Buddist will believe otherwise. Since the truths we find in this world apply only to ourselves, our planet, our galaxy, or even our universe, it's doubtful that it will apply to every being on every planet, in every galaxy, and every universe, should there be multiple universes.
The "truth" is what we say the "truth" is. The highest level of knowledge that we have is theory as we can not be sure of anything. We may call something a "fact" that is based upon a "truth". For example if I jump out of this window shall gravity fail? Gravity is only a theory yet we say it is very probable as it has proven to be. With gravity only being a theory however you cannot define it an absolute truth.
Philosophically speaking a "truth" quite often isn't. There shall never be a truly unbiased "truth". Is the bible pure truth or written by someone who is devoted to Christ? Is it biased? The probability is high.
Truth is usually defined by probability but there can never be a true "truth" that we know of.