There can't exist 'truth'. We, humans, aren't capable of observing the 'truth'. It's really simple.
Let's say you want to tell someone of a certain sighting. Even if you convey the information to said someone, the information is merely your own comprehension, thus it can't be 'truth'. It is your experience and understanding that you are forwarding, not 'truth'. And it can never be 'truth', as the true information you want to share is already corrupted by you. Thus, for humans, there will never be any 'truth'.
And that's by ignoring the fact that we simply miss so much information because our bodies limit us. For example, we can't see infrared or microwaves. We can't see how photons or atoms or molecules or cells act. And even when we use technology to 'look' how they work, the very technology we use warp our perspective.