Sri Aurobindo translates Shwetashwatara Upanishad, Chapter Five, Verses 8-9: “His size is as the size of a man’s thumb, but His aspect as the Sun in its glory; and He hath Volition and He hath Personality; but there is another whom we see by virtue of the Understanding and by virtue of the Spirit for the point of a cobbler’s awl is not finer to vision. Take thou the hundredth part of the point of a hair, divide it into a hundred parts again; then as is a part of that hundredth part of a hundredth, such shalt thou find this Spirit in man, if thou seek to separate Him; yet ’tis this in thee that availeth towards Infinity.”
It is not possible to perceive the embodied Spirit with the physical senses. Yet spiritual seekers find that the experience of the Jiva, the Eternal embodied in man, can be experienced. We are normally focused on the outer world and the perceptions provided by the gross physical senses. Our gaze is directed outwards. Those who seek spiritual realisation turn their gaze inwards.
Sri Aurobindo speaks of a “desire soul” which is the ego-being that we have created to interface with the outer world, as well as a true soul that is our portion of Eternity. The true soul is veiled by the focus and action of the desire soul. When we quiet the promptings of desire, we can, through intuition and an inner seeking, come into contact with the true soul.
The seers have described it as the size of a thumb, located behind the heart. This is not a physical description, but a transcription of the experience of the subtle nature of the psychic being of man. It is described as having a brilliant radiance “like the sun”. Through the process of quieting the outer being and concentrating inward behind the heart, the seeker can come in contact with the soul.
It is said that he has “Personality” and “Volition”. When we are fixated in the outer desire soul, we believe that all action only occurs under the impulsion of egoistic desire. But the Eternal manifests the universe without any need for fulfillment of such desires. The Eternal, the Infinite manifests all forms and beings because it is His Nature to do so. The true soul, as a portion of the Divine embodied in the heart of each being, partakes of the divine Personality and the divine Will that manifests.
Sri Aurobindo, The Upanishads, Shwetashwatara Upanishad, pp.369-384