James Mark Baldwin, answered from the texts and cited to the page.
There is no self locked in a private chamber that afterward learns, as a second thing, to deal with other people. The self is social from its first dawning, and it grows only in commerce with others. Watch the child: it builds its sense of what it is by taking in the persons over against it, imitating them, projecting into them the inner life it is just discovering in itself — I called this the ejective self — and finding itself, in turn, only as one such person among the others.1234
The sense of "me" and the sense of "you" rise together, each the condition of the other, in a single dialectical movement I named the dialectic of personal growth; the socius, the social self, is the real unit, not the solitary ego of the philosophers.5 What I am I have drawn from others and given back to them; my very selfhood is a deposit of the social relation.
To ask which came first, the individual or society, is to misread a growth in which the two are born together and neither is thinkable alone.
The child's subject sense goes out by a sort of return dialectic to illuminate the other persons. The 'project' of the earlier period is now lighted up, claimed, clothed on with the raiment of selfhood, by analogy with the subjective. The subjective becomes ejective; that is, other people's bodies, says the child to himself, have experiences in them such as mine has.Social and Ethical Interpretations in Mental Development, pp. 9–10
Again, it is easy to see what now happens. The child's subject-sense goes out to illuminate these other persons. The projective is now lighted up, claimed, clothed on with the raiment of self-hood, by analogy. The projective becomes ejective, i. e., other people's bodies, says the child to himself, have experiences in them such as mine has.Fragments in Philosophy and Science, p. 192
The project of the earlier period is now lighted up, claimed, clothed on with the raiment of self-hood, by analogy with the subjective. The projective becomes ejective; that is, other people's bodies, says the child to himself, have experiences m tJiem such as mine has. They are also me s: let them be assimilated to my vie copy.Mental Development in the Child and the Race, pp. 338–340
For it will be remembered that all these marks were at first actually taken up by imitation from these very persons. The child is now giving back to his parents, teachers, etc., only the material which he himself took from them.The Story of the Mind, pp. 90–91
Looking at these requirements together, and attempting to discover what sort of a general movement will result, we find what may be called the ' Dialectic of Social Progress Social Growth,' an expression which is intended to suggest an analogy with the ' Dialectic of Personal Growth/ already described. 2. Dialectic of Social Growth 338.Social and Ethical Interpretations in Mental Development, p. 512
This is among Baldwin's most influential and most vindicated ideas. His social self directly shaped George Herbert Mead's account of the self arising through taking the role of the other, prefigured Vygotsky's thesis that higher mental functions are social in origin, and anticipated the whole social-constructionist and relational tradition in the psychology and philosophy of selfhood. The standing objection is the individualist one: that some minimal pre-social capacity — for attention, imitation, the discrimination of persons — must be presupposed as the thing that does the social taking-in, so that the self cannot be social "all the way down." Baldwin's answer is that these capacities are precisely what the dialectic develops, not a finished pre-social ego; the debate over how social the self is at its root remains alive.