There are many standard definitions of Ātman but the most substantial has to do with Its Essential Selfhood. Standing alone as the First Principle, It is the Real-Self that at once transcends all phenomena while simultaneously serving a supportive function as the Essence that constitutes the very fabric of all Beingness. In this respect, it connotes the flavor of a most salient Upaniṣadic recipe:
What is the Upaniṣadic ātman? The ātman is not the individual ego; it is neither the body nor the totality of the psycho-physical elements which make up the empirical individual. It is the “inner-ruler” (ataryāmin) which resides in the universe but is distinct from and unknown in the Universe. It is the “inner-light” (antarjyotis) of man. (Kamaleswar Bhattacharya, The Ātman-Brahman in Ancient Buddhism, pg. 5-6)
This is the definition of the Ātman as it is In Itself; there is an empirical form, however, and it’s this form that gets most people in trouble. This corporeal sense is mortal and experiences all there is in samsara but it is distinct from the incorporeal ātman which is immune to all carnality, or the Self-Supreme:
The Buddha did not say, “There is no ātman.” He simply said, in speaking of the skandha/khandhas, ephemeral and painful, which constitutes the psycho-physical being of a man: n’etaṃ mama n’eso ‘ham asmi, na m’eso attā, “This is not mine, I am not this, this is not my ātman. (ibid, pg.6)
In light of this we can clearly distinguish an authentic Real-Self, and an empirical self. The Real is aligned with the Absolute and Unchanging, the Spiritual Ātman of the Upanishads. Its lesser empirical function connotes the psychophysical attributes of the skandhic apparatus: form, thought, sensation, mentation and mortal consciousness. Another passage from the Pāli canon quoted by Bhattacharya also reinforces the assertion that the Buddha never denied the Authentic Self (Ātman), one that has been referenced time and time again here in the blogs at Unborn Mind Zen—from the Udāna:
There is, monks, an unborn, unproduced, uncreated, unformed. If there were not, monks, an unborn, unproduced, uncreated, unformed, there would be no issue [escape] for the born, the produced, the created, the formed. (Udåna, 8.3)
Bhattacharya delivers support for this passage based the Saṃyutta Nikāya:
Note that the “unborn, unproduced, uncreated, unformed” (ajāta, abhūta, akata, asaṃkhata), in a word, the Unconditioned, is not another world, situated beyond the “born, produced, created, formed” (jāta, bhūta, kata, saṃkhata). It is in us, is our very selves: it is our essential nature. It must, then, be discovered in the depths of our being, by transcending our phenomenal existence. (ibid, pg.47)
He therefore argues that neither the Upanishads nor Buddhism denies the individuals empirical reality (the world is a concrete intellectual synthesis highly visible and touchable); what is denied is its “ontological substantiality.” It cannot stand on its own since it is Self-empty. So the goal is not to achieve empirical complacency, but to soar like nuclear birds into the disencumbered sky of Universal Beingness—in effect, to put on the Ātman just as Bankei would say, to put on the Unborn Buddha Mind.