Suppose we define ‘self’ as the boundary between internal and external worlds. Its social function then is to manifest the individual person in the social milieu; but this also means concealing the primal person behind the mask of individuality. Now suppose that primal person is the deeper self as ‘inner world’: how primal is it? In Peirce’s evolutionary cosmology, it goes all the way back to the beginning:
The distinction between the inner and the outer worlds antedates Time. I do not mean by the inner world that human consciousness which Baldwin and Royce have lately so forcibly reminded us is a social development and therefore very recent, only now in fact in process of taking a shape which has not yet been attained. The inner world that I mean is something very primitive. The original quality in itself with its immediate unity belonged to that inner world, a world of possibilities, Plato’s world. The accidental reaction awoke it into a consciousness of duality, of struggle and therefore of antagonism between an inner and an outer. Thus, the inner world was first, and its unity comes from that firstness. The outer world was second. The social world was logically developed out of those two and the physiological structure of man was brought to forms adapted to that development.
— NEM 4, 141 (probably 1898)
Peirce is here proposing a co-evolution of a ‘the social world’ and the physical form of humanity – a more daring and comprehensive hypothesis than the co-evolution of language and brain as advanced by Deacon (1997), for instance. The logical development of the social world is the continuing evolution of Thought in the Peircean sense, of Thirdness mediating between the Firstness and Secondness which it involves, for ‘everything is involved which can be evolved’ (CP 4.86). Insofar as humanity is engaged in learning from experience, it continues to evolve through collective pursuit of the truth we hope to arrive at consensually.
This ultimate destiny of opinion is quite independent of how you, I, or any man may persist in thinking. It is thought, but it is not my thought or yours, but is the thought that will conquer. It is this that every student hopes for. It is the Truth; and the reality of this truth lies, not at all in its being thought, but in the compulsion with which every thinker will be made to bow to it, a compulsion which constitutes it to be exterior to his thought. If this hope is altogether vain, if there is no such compulsion, or externality, then there is no true Knowledge at all and reasoning is altogether idle. If the hope is destined only partially to be realized, then there is an approximate reality and truth, which is not exact.
MS 735, “The Theory of Reasoning,” undated (quoted in Kaag 2014, Kindle Locations 2034-2036)