In his book “Messages to Mankind” Swami Chidananda writes:
The true basis of human unity where all beings are at one is the factor that is the essential being within us. Superficial factors express diversity; there is a difference. In form all are different. Diversity, more than unity, seems to be the law of creation. In everything, everywhere upon the face of the earth, we find diversity. No two leaves are alike but even though a tree is full of diversity, and is full of diverse branches, twisting twigs, leaves, flowers, fruits, etc., is rooted in unity. The root is one; the tree springs from oneness. So, if you trace all diversities to their source, the apparent diversity is found to be based upon unity, based upon oneness, having a singleness of source. There could no more be an apt analogy to bring home to us the truth of oneness of mankind than that of the tree with its diverse branches, shoots and twigs being founded upon the one, viz., the root.