Wait so does this truth exist, or is it also a lie on some level?
It's not truth at all. Just an observation. It happens to fit with my perceptions. That's it.
You can artificially define truth by tying it to a particular frame of reference, but that's not "the truth", as that frame of reference is not 100% transferable to others anyway. The idea of umwelt, as I understand it, seems to work here. Still, it's just an observation, an impression.
I'm not really saying anything new here. Descartes was saying something similar quite a long time ago. Then again, he could have meant something else entirely and there's no way for me to know which is it. I just assume my understanding is close enough to the intended meaning. I may well be completely wrong on this.
Basically, there's nothing you can be really sure about, including the fact that you can't be really sure about anything. There are only things that appear to work for you and, possibly, others. You can use them. Just don't believe them unquestioningly.
Some simplifications are useful in some contexts, but the world is an unimaginably complex thing and trying to dumb it down can only take you so far.