In this article the following views based on the development of human knowledge about the universe are expounded: (1) In space the universe is infinite, infinitude nevertheless cannot exist by itself independent of things finite. Infinitude and finite-ness form a unity of opposites. Finiteness transforms into infinitude, infinitude transforms into finiteness. All the various versions on the infinitude and the finite-ness of the universe that existed in history, from Newton's classical model of the universe to modern cosmology, cannot lead to a correct knowledge of the dialectics of infinitude and finiteness; thus, as a consequence, they all degenerate into metameta-physics and idealism. (2) In time the universe is also infinite. Matter in the universe is in incessant development. The totality of the universe has neither beginning nor end. The theory of a motionless universe is unsound. It is a far-reaching realization in the development of human knowledge of the universe that the universe is a unity of such opposites as absolute infinitude and relative finiteness.