This is a basic idea in Marxist philosophy. Marx believed that practice is the only criterion for testing truth, that is, truth is verified through practice. He believes that through practice, people can explore their own knowledge and truth, and constantly revise and improve their thoughts.

Marx proposed this idea in "Das Kapital". He believed that human knowledge is obtained from practice, and only through practice can knowledge be truly understood and mastered. Therefore, he believes that practice is the only criterion for testing truth.