“The existence and influence of other worlds are a fact of primary importance for the possibilities and for the scope of our evolution in terrestrial Nature. For if the physical universe were the only field of manifestation of the infinite Reality and at the same time the field of its whole manifestation, we should have to suppose that, since all the principles of its being from Matter to Spirit are entirely involved in the apparently inconscient Force which is the basis of the first workings of this universe, they are being evolved by it here completely and here solely, without any other aid or pressure except that of the secret Superconscience within it. There would then be a system of things in which the principle of Matter must always remain the first principle, the essential and original determining condition of manifested existence. Spirit might indeed in the end arrive to a limited extent at its natural domination; it might make its basis of physical matter a more elastic instrument not altogether prohibitive of the action of its own highest law and nature or opposed to that action, as it now is in its inelastic resistance. But Spirit would always be dependent upon Matter for its field and its manifestation; it could have no other field: it could not get outside it to another kind of manifestation; and within it also it could not very well liberate any other principle of its being into sovereignty over the material foundation; Matter would remain the one persistent determinant of its manifestation. Life could not become dominant and determinative, Mind could not become the master and creator; their boundaries of capacity would be fixed by the capacities of Matter, which they might enlarge or modify but would not be able to transform radically or liberate. There would be no place for any free and full manifestation of any power of the being, all would be limited for ever by the conditions of an obscuring material formation. Spirit, Mind, Life would have no native field or complete scope of their own characteristic power and principle. It is not easy to believe in the inevitability of this self-limitation if Spirit is the creator and these principles have an independent existence and are not products, results or phenomena of the energy of Matter.”
Here Sri Aurobindo has succinctly made the case for the independent existence of worlds of Spirit, Mind and Life independent of the limitations imposed by the worlds of Matter. There is essentially no explanation of how the higher powers can evolve in Matter if they do not have their own independent existence and principles, and therefore, their own worlds within which they can express their native powers.
Sri Aurobindo, The Life Divine, Book 2, Part 2, Chapter 21, The Order of the Worlds