Things in general exhibit unity in a wide range of degrees. The kinds of unity that are possible for simple things are different from those that are possible for complex things.
Plato compared the human psyche to a city. This certainly implies more coherence than that of a mere collection, but it also implies somewhat less coherence than that of an organism.
The traditional folk psychology of many cultures distinguished layers or components of the psyche with nontrivial degrees of relative autonomy. Medieval Christian theology was somewhat unusual in emphasizing a very strong unity of the soul. For the theologians, a strong unity of the soul was at once a moral wish, an object of faith, and a discursive result of a vigorous tradition of introspective psychology that was also influenced by faith.
Through Descartes, this strong unity acquired a new destiny of a more secular sort, in new implicit claims that the empirical psyche naturally has the same very strong unity the theologians had wanted for the soul. Descartes effectively presented this as an immediate natural intuition, independent of faith and independent of discursive argument. Meanwhile, his account of psychology was very truncated and impoverished.
(Despite its iconic status, Cartesianism never held Western philosophy in a hegemonic grip. To mention but one example of an alternative, Locke — for whom I have little affinity, but whom I take quite a bit more seriously than Descartes — greatly developed the idea of immediate natural intuition Descartes had relied upon, but without making such strong claims about the unity of the empirical psyche. Locke’s notion of personal identity was based on actual concrete continuity of memory. While this might be criticized as reliant on a kind of immediacy, it is not the sort of sheer presumption or rabbit out of a hat that Descartes had on offer. Locke’s epistemology was also foundationalist, but in other ways it was more modest, and his psychology was much more richly detailed.)
At any rate, I now want to at least begin to make explicit what ought to follow about the sort or degree of unity of the empirical psyche from what I have been writing in these posts.
The empirical psyche would be the seat of what I have called feeling and of Aristotelian acquired character or emotional disposition, as well as of Kantian intuition, physical sensation, and general sentience; and of our acquired second nature as talking animals. It would be the common-sense referent of an empirical-factual “me”.
As sapient talking animals, our acquired second nature nominalizes the empirical psyche’s participation in a socially, historically, and linguistically constituted Kantian transcendental field that would be the home of values, ethics, Thought, Reason, unities of apperception, Aristotelian intellect, Hegelian Spirit, and Brandomian scorekeeping. Things of this sort are involved with time, but not in the same way as empirical things. Like empirical things, they evolve diachronically, but they also have much more extensive acquired synchronous structure. As the index of the unity of a unity of apperception, a philosophical “I” has this character. With respect to the sort of individuation conferred by empirical facts, this “I” is completely anonymous. It is nothing in itself, but metonymically identifiable with all things or, more precisely, with anything or everything in a unity of apperception it indexes. This philosophical “I” is the rational ground of the “I” of ecstatic poetic identification.
Nonmental, inferential-relationally constituted Essences or Forms or shareable Thoughts are the real bearers of normative Subjectivity. A philosophical “I” just nominalizes something like the ecosystem or community of shareable, interacting Thoughts in a unity of apperception or piece of Hegelian Spirit. The empirical psyche provides a kind of place where these things happen, and a kind of embodiment of that happening. The psyche is not a Subject, but a place where some precious Subjectivity may happen and get embodied. “I” am not that place, that “me”, but rather the transcendental “ecosystem” that lives in that “me”. Part of the same transcendental ecosystem — values and inspiration and Thoughts and spiritual love — that lives in “me” may also live in “you”. “We” are not mutually exclusive entities, and that is part of our social essence. (See also What Is “I”?)