how to know "right" is right!

Inspired by 怎知對是對

so far, human can only deal with logic in mathematics to prove somethings right or wrong in a consistence structure/system. or you can call it "proof is contained". (in fact, the Gödel's incompleteness theorems stated that there are somethings cannot be proved even in mathematics!)

For things not within the kingdom of science, there is nothing right or wrong. only popular or not, eyes catching or not. an example is the Marx's communism, he said that it is "logical", "scientific", but when you look at the arguments, it is simply a set of opinions without or cannot be proved. the so called "social science", is nothing science at all, or, a weak science. why? because they use hundred and thousand of assumptions. Comparing with social science with mathematics, physics or some what strong science, we can see that those are only based on few assumptions. take the Euclid's Elements as an example, the book 1 only has 23 definitions and 5 postulate, and by these, the whole set of 2nd school geometry was built.

in my opinion, we only have few things can be said "right" or "wrong", coz most others are not subject to prove! so, if we want to know "how to know right is right", we have to ask it within an area that "right" or "wrong" is well-defined.