Taking a single underlying entity and treating it, under a fixed role or aspect, as a distinct derived bearer of properties with its own narrower existence conditions. The person-as-employee is a genuine item — it carries duties, has a life-cycle, and ceases to exist when the employment ends — even though the person persists.
Your mom is one person, but she plays different parts. As your mom she tucks you in; as a teacher at school she gives homework; as a driver she has to stop at red lights. She's still one person, but each 'part' she plays comes with its own rules. What's true of her as a teacher might not be true of her as your mom.
Facts Stick To The Hat
An Aspectual Individual is when you take one thing and treat it as a different 'property-holder' depending on which role it's playing. The same person as an employee has work rules; that same person as a taxpayer has tax rules; that same person as a parent has family duties. It's all one underlying person, but 'the person-as-employee' is its own item with its own life: when the job ends, the employee-role ends, but the person doesn't. The neat test: can something be true of the person in one role that isn't true of them plain and simple? If so, you're dealing with an aspectual individual. It stops you from wrongly assuming that what she did 'as president' she also did privately.
The Entity-Under-A-Role
An aspectual individual is the move of taking a single underlying entity and treating it, for a specific purpose, as a different bearer of properties once a role or aspect is fixed. The same person as employee bears one bundle of rights; as taxpayer another; as parent yet another. The underlying individual persists, but 'the person-as-employee' is a distinct item with its own life-cycle and its own conditions of existence. There are five commitments: a base individual whose identity persists across aspects; one or more aspects (roles, contexts, modes of presentation) applied to it; each aspect-qualified item being a derived but genuine bearer that can take on properties and relations; the aspect-qualified item having narrower existence conditions than the base (the person-as-employee ends when the job ends, the person doesn't); and properties of one aspectual individual not necessarily transferring to another or to the base. The sharp test: can a property be ascribed to the entity-under-an-aspect that doesn't transfer to the entity plain? If yes, an aspectual individual is in play — which blocks inferring from 'she, as president, signed the order' to 'she, privately, signed the order.'
An aspectual individual is the structural move of taking a single underlying entity and treating it, for some specific purpose, as a different bearer of properties once a role, aspect, or mode of presentation is fixed. The same person as employee bears one bundle of rights and obligations; the same person as taxpayer bears another; the same person as parent yet another. The underlying individual persists, but the aspect-qualified bearer — the person-as-employee — is a distinct item with its own life-cycle, its own properties, and its own conditions of existence. The structural commitments are five. There is a base individual whose identity persists across aspects. One or more aspects — roles, contexts, modes of presentation — can be applied to that base. Each aspect-qualified item is a derived but genuine bearer: it can acquire properties, enter relations, and be referred to as such. The aspect-qualified item has narrower existence conditions than the base: the person-as-employee ceases to exist when the employment ends, while the person does not. And properties true of one aspectual individual need not be true of another, nor of the base — which blocks the inference from 'she, as president, signed the order' to 'she, privately, signed the order.' The structural force is the localization of properties to the aspect under which they hold. By treating the entity-under-a-description as a derived bearer rather than as the base itself, the pattern lets one underlying thing carry many independent property-bundles without contradiction. The distinguishing test is sharp and substrate-neutral: can a property be ascribed to the entity-under-an-aspect that does not transfer to the entity simpliciter? If yes, an aspectual individual is being manipulated. The aspectual individual is not a separate physical entity, not a mere linguistic predicate, and not the base itself; it is the entity-under-a-description treated as a full bearer with its own properties, and this move recurs identically across philosophy, law, software, sociology, and diplomacy.
Lets you see that aspect-bound bearers are not paraphrases of the base entity but full items, so the disambiguating question before any property-ascription is "in what capacity?".
Localizes properties to the contexts where they apply, so each context reasons about its own aspect-bound bearer and imports only relevant properties, sparing the base the impossible task of bearing every role's properties at once.
Lets predication be relative-to-an-aspect without becoming merely relative to a sentence — the property is borne by a genuine derived item, which is what gives the aspect-bound bearer its own existence conditions.
Philosophy to law: the qua-object move underwrites the corporate veil — a liability of the corporation-as-employer must not be inferred to a shareholder simpliciter.
Philosophy to software: the same structure is interface polymorphism, where one object exposes only the responsibilities of the role it is addressed under.
Across domains: the discipline — name the base, name the aspect, refuse the inference from one aspect to the base or a sibling — prevents property-leakage everywhere.
The statue and the lump of clay share one material base, but the statue-aspect "is destroyed by flattening" while the lump-aspect "survives flattening" — non-inheritance blocks the contradiction, letting one material thing carry incompatible modal property-bundles.
Aspectual Individual is not a Role because a role is a position with role-generic expectations that survive a change of occupant, whereas the aspectual individual is the occupant-considered-under-the-role, carrying occupant-specific properties that vanish when this occupant leaves.
Aspectual Individual is not Essentialism because essentialism concerns which properties are necessary to a kind, whereas aspect-bound properties are precisely non-essential yet real and predicable.
Aspectual Individual is not an Institution because an institution is the standing rule-system that generates aspects, whereas the aspectual individual is the token-level base-under-the-aspect those aspects produce.