B: If there is such a thing as eternal truth, then the source of the knowledge of it must be God and not man.
B: Because men are fallible; they don’t know everything about the universe, nor its beginning, nor its end. They therefore cannot decide if and when truth changes. It’s not like people can just vote on something to decide whether it is an eternal truth, simply because nobody can know, of themselves, what truth is and when (or if) it changes.
B: No, science consists of a bunch of man-made observations, assumptions, and conclusions. It is precisely because they are made by man, and not by God, that they cannot be guaranteed to be eternal truth. But I’ll discuss more about this later.
I need to explicitly state the following (cue grand music, please):
Assumption. Some eternal truth exists.
A: Whoopee. What’s the big deal?
B: Well, here’s my (strike it up again, Bob!)
Justification. Let’s suppose that there’s no such thing as eternal truth. I claim that this reduces life again to the same purposelessness we encountered while assuming there was no God. Because if there is no eternal truth, then all truth must change at some time or another, and how would we know if or when it changes? As indicated before, we could only determine that from God.
So suppose you’re tempted with the idea of doing something bad. On the one hand, you want to succumb to temptation, but on the other hand, you feel you shouldn’t. “Bad?” “Shouldn’t?” If we’re ever using words like those, we must be appealing to some kind of moral authority, the ultimate being God. Well if no truth is eternal, then all truth is relative, and how can you know whether or not even the very truth concerning the existence of a moral authority has changed? If there is no way to know that, then it doesn’t matter whether or not you do the “bad” thing – it may or may not even be “bad” anymore!
Therefore, we could never judge any of the actions we take to be “good” or “bad,” as we wouldn’t know whether or not the truth concerning the matter has changed by the time the choice to take those actions is presented to us. We would be entirely unable to affect the moral barometer of anybody’s life, including our own. Recall that if there is no morality, there can be no purpose; hence, no choice anybody makes would ever matter, and the entire existence of life anywhere for anybody is pointless.