The answer to why a child is not a fish is idealistic is as follows. It is not accurate to say that children are not fish. Generally speaking, idealism holds that truth and law exist only in people's minds, and matter is the product of this consciousness. Zi Feiyu believes that "Mozi's way lies in the heart", and Mohist thought pays attention to practice and emphasizes the combination of theory and practice. So Mohist philosophy is closer to pragmatism and instrumentalism than idealism.