A good argument is built on good data and premises. The further we move away from "Justified True Belief", aka knowledge, the more error-prone our conclusions are likely to be.
Accumulating Justified True Beliefs are achieved by reducing potential errors in data and reasoning.
A Justified (but not True) Belief can fail to be true for at least 2 reasons: 1) because we lack the evidence or awareness of the evidence to justify the actually true belief, or 2) because we have chosen poor justifications, such as logical fallacies.
Logical fallacies are reasoning that have provably failed to determine the truth of a hypothesis or belief, and are therefore not useful for determining the truth. Example: "Well Socrates thought the sun revolved around the earth, and he was a smart guy." Fallacy: appeal to authority.
We cannot achieve perfectly Justified True Belief without having perfect knowledge. Therefore every attempt at JTB is just a JB and should be open to revision as we improve our evidence and reasoning.
A True Belief, while true, is indistinguishable from a False Belief if it is not justified. Just as many once thought the sun rotated around the earth and believed fire is hot, we can have true and false beliefs. We need justification to separate the wheat from chaff.
but I don`t know why assumptions are something bad or contrary to true believe ? When I say the water is blue, the grass is green, the tree is brown etc. and a lot more. Why is it bad ? I think the mistake are metaphysical premises but not assumptions.
Grass is green is a statement justified by experience. It also can be justified by measuring the wavelengths of light it reflects. Those statements are not an example of True Belief lacking justification. You can't actually give me an example, because we can't know its true without justification.
is only word-play: when I say, the water is blue, then I make a assumption (Behauptung). So, we make very many of them. And that`s not wrong. I know, because we can justify them. But the richness of assumptions don`t make the world unbelievable (they aren`t metaphysical assumptions).
Aside from being effective, we can simply want to develop a more accurate view of the world for the love of understanding. For the pleasure of curiosity and the love of truth.
Mystery is usually nice due to the promise of the thrill of discovery, or do to fear of knowing the truth. The first shows that mystery is just an intermediary step toward understanding, and the second is an unfortunate and probably unhealthy condition.
Those who have an accurate understanding of the world are more capable at navigating dangers and effecting change. Meteorologists who don't understand what temperatures cause rain to become snow are going to be less effective at their job than those who do.
who want not something better ? A good question is this. Why should we investigate further ? Even better: Should we investigate further? Your question suggest positive answers.
Edit: You ask "why should we want to understand the world ´better`?" So you suggest (because of the `better´) a positive answer. If you erase the word `better´ you have this: "why should we want to understand the world." This is more neutral. Because know I could say this...
I don`t know how the knowledge of black holes, lead to more empathy. Nor the knowledge of psychological priciples, or something like that. Empathy is based on sympathy, sympathy is based on subjective evaluation, but not on facts. Even this fact doesn`t lead to more empathy.
Not all knowledge directly contributes to empathy, but better understanding the range of human experiences, the power of psychological traps, and how to more effectively help people all does.
Please use charitable interpretations of the argument, else we waste everyones time.
but JB could also leads to the other way, to less empathy. (The notion of Determinism, the notion of philosphical zombies, the denial of free will). That doesn`t make your statement untrue. But it is warn sign. We shouldn`t euphemize JB.