Individuation might be said to have two sides, unity and particularity. I would rather say coherence and specificity. What are called individuals are generally complex wholes, not true atoms; and to the extent that they are definite and subject to understanding, they are something more than mere particulars.
As this applies to people, I have been arguing that the unity of personality or self should be expressed as some intermediate degree of coherence — what the Platonists called a One-and-Many. If we are being really precise, empirical “me” is never exactly the same as it was yesterday, even though there is a very strong family resemblance. Empirical “me” also has many different tendencies and aspects, with some degree of tension and inconsistency. Lockean continuity of memory too is a matter of degree; memory is malleable and incomplete.
I recently read some phenomenologist praising the idea of a “one-level model of consciousness”. That sounds horrible to me, the complete opposite of the lessons of Kant and Hegel, mixing up the empirical and the transcendental and ignoring the fact that differentiation is what gives meaning and form. (See also Empirical-Transcendental Doublet.)
While still feeling kinship with all life, I am fully won over to the importance of Brandom’s sentience/sapience distinction. Applying this to individuation yields interesting results. Sapience is not a kind of super-powered sentience that overcomes natural limitations. It is something wholly other, a social-historical-normative-linguistic transcendental field that natural sentience can nonetheless indirectly partially participate in, thanks to the mediation of second nature.
The formal “I” that indexes the transcendental field is in one way anonymous, but in another way more individual, more intimate, and a much stronger unity than empirical “me”. Empirical “me” is subject to Humean flux, while formal “I” is prone to ecstatic identification. If, extending the Platonic metaphor, each of these names a kind of community or ecosystem — one of empirical psychic tendencies, and one of shareable Thoughts — the ecosystem of shareable Thoughts in the zone of interaction will normally be more coherent than the associated ecosystem of psychic tendencies.
A synthesis of shareable Thoughts also turns out to be far more unique than a synthesis of purely private experience. “I” as unity of apperception has much sharper focus than the “me” of putative immediate awareness. My commitments say much more about who “I” am than my private experience says about “me”. (See also Psyche, Subjectivity.)