Sri Aurobindo translates Katha Upanishad, Second Cycle: First Chapter, Verses 12-13: “The Purusha who is seated in the midst of our self is no larger than the finger of a man; He is the Lord of what was and what shall be. Him having seen one shrinks not from aught, nor abhors any. This is That thou seekest. The Purusha that is within us is no larger than the finger of a man; He is like a blazing fire that is without smoke, He is lord of His past and His future. He alone is today and He alone shall be tomorrow. This is That thou seekest.”
The Spirit is One. Due to the distractions of the objects of the senses, we fail to pay attention to and recognise the Spirit within. These verses describe the spiritual experience of the seeker who recognises the Spirit, within himself and throughout the universal creation. The seeker who systematically withdraws his gaze from the outer objects and shifts attention inward, behind the heart, can come in contact with his soul or Atman. This is the seat of that consciousness of the divine within. This is not intended to deny the omnipresence of the divinity, but to aid the seeker in tuning himself to the existence and standpoint of the divine. The descriptions provided here are actual transcriptions of experience. The size designation, “no larger than the finger of a man” is intended to aid the practitioner in understanding that one must continually withdraw and move inward from the experience of the outer world, and the workings of the physical body and mind, to find and identify with the awareness of the soul, which is hard to distinguish easily for a mind focused on external stimuli.
The universal Spirit is master of the “three times”, past, present and future. When the seeker makes the conscious connection to the Spirit, he identifies with the divine and thus himself shifts from the “victim” of Time to the “master” of Time.
Sri Aurobindo, The Upanishads, Katha Upanishad, pp. 213-241, and Kapali Sastry, Lights on the Upanishads, pp. 104-129