We conceive Oneness in the sense of uniformity, and we tend to see diversity and multiplicity as the opposite of Oneness. We see everywhere around us innumerable forms with virtually infinite diversity. We can see underlying principles at work, but we nevertheless fixate on the variations of the forms. Differentiation is taken to such an extreme that every human being can be identified by individual fingerprints!
Sri Aurobindo points out that this once again represents “the logic of the Infinite.” “Oneness or sameness is everywhere, diffentiation is everywhere; the indwelling Reality has built the universe on the principle of the development of one seed into a million different fashions….because the essence of the Reality is immutably the same, it can assume securely these innumerable differences of form and character and movement, for even if they were multiplied a trillionfold, that would not affect the underlying immutability of the eternal Identical.”
and further “The immutability of the Identical does not consist in a monotone of changeless sameness incapable of variation; it consists in an unchangeableness of being which is capable of endless formation of being, but which no differentiation can destroy or impair or minimise. The Self becomes insect and bird and beast and man, but it is always the same Self through these mutations because it is the One who manifests himself infinitely in endless diversity.”
While we struggle with this and try to impute an air of illusion or unreality to the innumerable forms, the logic of the Infinite is able to bring together the Oneness and the Diversity as aspects of the One Reality, and the power of this vast display of different forms is that it is all inevitably still that “One without a Second.” This is known as the power of Maya, the power to manifest the “logic of the Infinite” in infinite forms.
reference: Sri Aurobindo, The Life Divine, Book 2, Part I, Chapter 2, Brahman, Purusha, Ishwara–Maya, Prakriti, Shakti, pg. 340