The Upanishads, in describing the Supreme as “not this, not that” are attempting to remove from our minds the limitations of a fixed form or definition, because the Supreme transcends these forms. This is not to say that there is an opposition between the Divine and the creation, as many religious traditions have taught, but that the Supreme simply cannot be confined solely in that form or definition. It is a liberating statement that does not restrict the Divine from taking all forms, but ensures that we do not get caught up in a specific form to believe that we have understood the deepest and the highest truths and Reality.
At the same time, the Upanishads make the apparently opposite statement that “All this is the Brahman.” This statement is not meant to oppose the liberating statement but to complement it. While we need to recognize the transcendent character of the Divine, beyond limitation by any specific form or force, we should not forget that each and every form and force is a manifestation of and expression of the Divine.
Thus, when individuals worship a particular form, a particular God, a particular aspect, they are worshipping the Divine, and the fruits of that worship eventually come to them. To the extent that they worship one particular God, however, they limit the ultimate and complete realisation that extends far beyond any one God.
The seeker of the ultimate Reality, the absolute Truth, therefore, goes beyond the expressions of any one religion without at the same time, denying the truth implicit within that religion. As Sri Aurobindo points out: “All sincere religious belief and practice is really a seeking after the one supreme and universal Godhead; for he always is the sole master of man’s sacrifice and askesis and infinite enjoyer of his effort and aspiration.” The limitation is that “…the fruit of the adoration and offering is according to the knowledge, the faith and the work and cannot exceed their limitations, and therefore from the point of view of the greater God-knowledge, which alone gives the entire truth of being and becoming, this inferior offering is not given according to the true and highest law of the sacrifice.”
To achieve the highest one must therefore transcend the limited forms in one’s seeking and worship: “An entire seeing of the Divine is the condition of an entire conscious self-surrender…” “But to follow after the supreme and universal Godhead alone and utterly is to attain to all knowledge and result which other ways acquire while yet one is not limited by any aspect, though one finds the truth of him in all aspects.”
Sri Aurobindo, Essays on the Gita, Second Series, Part I, Chapter 6, Works, Devotion and Knowledge, pp. 317-318