Why did the king of Portugal reject Columbus’s project? What arguments could Columbus use to convince the king?

By the end of the 15th century, Portugal had mastered the eastern route to India, so the Portuguese did not need a new western route. If Columbus had convinced himself and others that there was another equally rich land in the west, then perhaps the Portuguese would have supported him.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.