Truth, real truth, never changes - which is why it is so important to be slow to declare it. Our best collective understanding at a particular time is exactly that, but that is different than truth or fact, because often that understanding turns out to be wrong, which is why it is so crucial that dissenting opinions are heard.
An actual unchanging truth is extremely beneficial for planning. But if you're planning with open eyes, you know that what you actually have are probabilities based on what you know when you make the plan, which I believe to be GP's point.
Anyway, there's no other definition of "truth" that isn't a mockery of the word as used. In practice you work with the closest you can get at the moment, but you don't redefine your terms down to match.
The absolute truth in your statement is the threat of getting burned alive. You make the decision to escape based on that absolute truth and then you choose the route based on relative probabilities to survive. But you wouldn't even be trying to escape at all if not for the absolute truth that a fire will kill or severely harm you if you stay.