1 and barber paradox, also known as Russell paradox, were put forward by mathematician Bertrand Russell in 190 1. Paradox content: The only barber in a city can only cut the hair of all people who don't cut their own hair. Should he have his hair cut? A: This city cannot exist. Because (1) if the barber doesn't cut his own hair, he needs to obey the rules and cut his own hair; (2) The barber cuts his own hair, but he can't cut it himself according to the rules. (This paradox is due to the unlimited definition of elements in Huai Su's unification theory. At that time, set theory was called the foundation of mathematical theory, and the appearance of this paradox directly led to the third mathematical crisis, which triggered the current axiomatic set theory and prompted mathematicians to realize the necessity of axiomatization of mathematical foundation.

2. If God is omnipotent and knows what we will do before we are created, how can we feel free? Answer: This paradox can be explained by the fact that God exists outside time-he can know the future just as he knows the past and the present. Just as the past will not interfere with our free will, so will the future.

A crocodile stole a father's son. He promised that he would return his son to his father if he could guess what he was going to do. So what if the father guesses that "the crocodile will not return his son to him"? Answer: If the crocodile doesn't return his son, then the father guessed right and the crocodile broke his word. If the crocodile returns his son to him, then the father guessed wrong and the crocodile broke his word.

A man went back to the past and killed his grandfather before his grandmother saw him. This means that one of this person's parents will not be born; Conversely, this person will not be born himself; This means that he has no chance to go back to the past; This means that his grandfather is still alive; This means that this man can imagine going back in time and killing his grandfather. Answer: When a time traveler changes something in the past, the parallel universe will be cut open, which can be explained by quantum mechanics.

5. There is a pile of 1000000 grains of sand. If we take a grain of sand, there is still a pile of sand; If we take one more grain of sand, it will still be a pile. If we only take one grain of sand at a time, is it still a pile when we only get one grain of sand? Answer: Set a fixed boundary. If 10000 grains of sand are a pile of sand, then less than 10000 grains of sand cannot be called a pile of sand. Then it is a bit unreasonable to distinguish 9999 grains of sand from 1000 1 grain of sand. Then there is a solution-set a variable boundary, but you don't have to know what the boundary is.

6. Can God create something that is too heavy for him to lift? Answer: If he can, then he can't lift this thing, which proves that his strength is not omnipotent. If he can't create such a thing, it proves that he is not omnipotent in creation. The most common answer is that God is omnipotent, so "lifting" is a meaningless condition. Others pointed out that the question itself is contradictory, just like a "square circle".