Kutastha is another name for the akshara (imperishable). The term is found in the Bhagavad Gita (XIV – 16), and later in Panchadasi of Sage Vidyaranya (VI-22.23). Adi Shankaracharya commenting on this stanza of the Bhagavad Gita, observes that Kutastha is one who does not change or perish.
Vidyaranya seems to have understood it as the immutable, immovable being. It is like the anvil on which the blacksmith works to change every iron piece, while keeping the anvil itself unchanged.
It is held that the self in the midst of changes remains changeless and that all changes take place only in contact with it and this is what is suggested in the form of the metaphor.
It may also signify the top of a mountain, which remains unchanged and undisturbed despite changes taking place around it.
According to some scholars the word kuta stands for the changeable world while the unchangeable exists within it, as circles within circles, projecting both the perishable and the imperishable reality.
Since Shankaracharya and his followers have identified all things constituting the field of matter as nothing other than the Supreme Self, they argue that the bars, the wire, the bits and the rings made of gold are only different forms of the same gold.
Ramanuja and his followers opine that on the same ground the changeable are to be considered the amsha (parts) of the Supreme in the aspect of creation.
Since two purushas are referred to in the stanza of the Bhagavad Gita, Ramanuja, commenting on the same, holds that kshara in the context refers to the bound selves and akshara to muktas, the liberated ones.
Akshara, or the liberated souls, form one of the three types of souls, the other two being nityas (eternal) and bandha (bound). They who obtain the Lord’s grace by following the path of bhakti and surrendering unto Him live in the Paramapada or Vaikuntha.
Source – Encyclopedia of Hinduism volume VI – page 215 – IHRF
Akshara, A Forgotten Chapter In The History Of Indian Philosophy (1932) – P.M. Modi – The Baroda State Press, Baroda.