Philosophy is intended to systematically and rationally answer questions such as "What is existence, what is life, human, society, truth, the meaning of life..." for the sake of the answer to the fundamental worldview question: "What are the criteria for a right life?"
Why can the question 'What are the criteria for a right life?' be considered the main question of philosophy? Because modern philosophy, recognizing naturalism and physicalism, in general possesses satisfactory answers to the other main eternal questions.
Who and what am I? What is life? Is life worth living? What compels me to live? What does it mean to live a 'right life'? How to lead and conclude life with dignity? What is the best that future generations can hope for?
