Chapter 1 Verse 12 - All pervading
The soul is witness, all-pervading, infinite, one, free, inert, neutral, desire-less and peaceful. Only due to illusion it appears worldly . ॥12॥
Most of the time soul is misunderstood to be personal. But it is never personal, it is impersonal or universal. There is only one soul which is non-dual. The properties of the soul are very important, as we are nothing but a soul in actuality. The soul which does not have birth and death is a eternal one. The properties of soul depicted in this verse, infact are not properties, since it can't belong to object. The soul is non-oject.
First of all we will understand soul being witness. In one of the verse we have explained what is witness. It is the one which can see as 'it is' without coloring of mind. A soul is witness therefore it is without individual identity, or individual mind. Its the universal mind. In fact consciousness, soul, whole, everything point to that non-dual truth, only named by different names.
The second property depicts that soul is all pervading, ie, it is omnipresent. It exist everywhere, there is not a single place in this universe where it does not exist. Soul is the essense of everything concivable by mind, or perceivable by mind. Therefore soul can't be conceptulised, perceived or conceivable.
The third property says soul is infinite. There is no start or end to soul. There is no birth or death to soul. Therefore it can't be more than one. Its one, its non-dual.
The person, who realises himself or herself as soul, aquires the freedom. Therefore soul is free. It is inert because it exists everywhere, therefore it need not move.
Whenever some one is enlightened, he realises himself to be soul. It is neutral, if it would have been non-neutral it can't be witness. Being neutral is the property of witness. It is desireless, because again it is witness, it cant be witness if it would have desires.
And since it posseses all of the above properties, it is peaceful.
And its the illusion which makes us to believe being body and mind, which is objective, or wordly.