Time, space and substance are the three categories of the mind. Every object has three kinds of limitations. Grapes, for instance, are obtainable in a certain season only and in certain places only. So grape has got limitation by space and time. It has got limitation by substance also. You cannot find grape in a mango tree. But, the existence of Brahman (Supreme Soul) is free from these three kinds of limitations, because He is eternal, infinite and the essence and support for all substances.
Brahman is free from the 3 kinds of difference which are i) the difference which appears between things of the same category, ii) the difference which appears between things of different category and iii) the difference which manifests itself in one and the same thing, either between its essence and form or between its component
parts. There cannot be another Brahman, because Infinity is One. So there is no difference which appears between things of the same category in Brahman. The world has emanated from Brahman. It is illusory. So it cannot bring the difference which appears between things of different category for Brahman. World is Brahman Himself. Sat-Chit-Ananda (Truth-Consciousness-Bliss) are not three entities. They are one. It is only sounds different. Sat is Chit. Chit is Sat. Chit is Ananda. So there is no difference which manifests itself in one and the same thing in Brahman. Difference is a mental creation produced by space, color, size, etc.
If anything is free from the three kinds of limitation of space, time, substance and three kinds of difference as described above, then it is termed Omnipresent. You can ascribe omnipresent nature to that substance. That nature can be attributed to Brahman only.
INQUIRY OF “WHO AM I?”
Liberation (release from the cycle of birth and death) comes through Jnana (knowledge of Soul or God). Jnana comes through right inquiry of ”Who am I?” or understanding and thinking of the right essential significance of the great sentence, “Tat Tvam Asi – Thou art That or You are That”. Inquiry of ”Who am I?” and understanding of “Tat Tvam Asi” are one and the same. Brahma-Jnana, which inquiries into the true nature of ”I” is the fire which destroys the mind.
It is the “Jnanagni – Fire of Wisdom” referred to in the Gita (IV-37): ”Jnanagnih sarvakarmani bhasmasatkurute tatha – The fire of wisdom reduces all actions (and the false “I”) to ashes. When any thought arises in the mind, inquire: Why has this thought wave arisen? Whom it concerns? Who am I? All the thoughts will die eventually. All mental activities will cease. The mind will turn inward. It will rest on Soul. This is spiritual practice. You will have to persist constantly in the spiritual practice whatever stray thoughts arise. The one thought “Who am I?” will destroy all other thoughts of worldly nature. That thought will die by itself. Ego will vanish. Balance left is pure consciousness which is free from all names and forms. That is Soul. That is to be known!
Mind – Its Mysteries and Control by Sri Swami Sivananda