Only because nobody has found a counterexample, it does not mean yet for a long time that a regularity must be fundamentally correct and generally valid.
Either because one does not know the true regularities of the world, (1) because there are none, (2) because they are possibly changeable, or (3) because one does not understand the nature of an entity to which this regularity should actually apply in detail, and this regularity does not apply, or only partially. So one can predict with no perfect security the result of a process, how something certain is built, actually nothing at all.
Everybody and everything alive has his own perception of the world which must be limited in some way, alone by this it is not possible to know something with absolute certainty, because in his own consciousness an image of the world is projected which the senses can perceive limitedly, which does not agree with the image of other beings, or because one lacks information which others have. Theoretically, I can not even safely assume that the readers here can understand my text, because his thinking apparatus works differently and can not understand human language.
Thus one can know nevertheless nothing with security, since the validity of this knowledge would depend on being able to be always applicable in this area, which it hardly ever does, always there are minimum deviations or exceptions, of which one does not know however often. Wouldn't one then have to know absolutely everything to be able to know anything at all with 100 percent certainty?
Observations depend also always on the observer and on the situation in which he was just, and also after thousands of observations and patterns which one can recognize, there could still be deviations from this pattern which would question everything before.
Can you not rely on anything 100 percent, not even logic (ok this one probably to a certain degree for sure), can you only hope that the highest probability is the safest possibility for, well, anything? And why do we still act as if all regularities were perfect without exception and we could know everything with certainty?
If not, then this would cause a fundamental problem, at first seemingly not that big of a deal if someone can be in best case 99.999...% sure of something, but if we look at the so called "human needs". For example, pick a person from the crowd of humanity and unfortunately of all things picked someone who is very different in nature than others, but we don't know yet; let’s ts say he hates to get hugged and let's say he hates being hugged or receiving other kinds of affection in general, not only that but gets physical damage from that (maybe he'll get a skin rash or something), good and healthy for most people but not for him. Most would argue one of those would be just mentally ill or has an unknown disease but when he doesn’t suffer otherwise I wouldn’t consider it a disease just because he is very different from the majority in this area. I mean there are a lot of psychological things the average person would literally die from, directly or indirectly, but are not called diseases, like not getting affection from your parents for example. But it poses the question if a century-long researched subject like human needs is flawed because not every human works the same way, maybe not completely wrong but not universally true either.
Another example: Let's say you're writing an essay claiming that "Every reader here is a male", raging women incoming complaining about how stupid this statement is, and sexist as well, and of course the statement is completly wrong. But what about you write instead, "every reader here has a brain in the head", then nobody would complain about this statement, because everybody thinks it would be a plain fact, until this one strange person arrives that can prove the author of the essay he has not a brain, rather a wide bodyspreading neurological network whose center is in the stomach, then the whole statement would be wrong as well, or at least not completly true, because there is an exception, this one of the let’s say one hundred thousand readers has got no brain in the head, but was it dumb to assume its a universal fact?
Thats the main problem, aside from as said earlier that no being can percieve the real world in its entirety in the first place, so no one can perceive the full objective reality and no one can really comprehend and understand it, if there is even one...