Modal Agency: Constraints, Affordances, and Self-Constructing Harnesses

The biological-autonomy tradition has made standard three conditions on agency: individuality, interactional asymmetry, and normativity. We argue that each is constituted rather than merely limited by a constraint, so that the discriminating question is not whether a system is constrained but whether its constraint structure fixes a single stable state or opens reliable paths to several. Those paths we call affordances and the stable states in which they terminate attractors, a distinction the affordance literature does not consistently draw; under assumptions we make explicit, empowerment measures the latter, so that a constraint enlarges agency insofar as it enlarges the set of afforded states. Agency so construed admits two independent dimensions, the breadth of what a fixed organization affords and the depth at which a system acts upon the structures generating its affordances, and, at the limit of depth, a third condition we term modal closure: a kernel-preserving fixed point at which the constraint structure affords its own reconstruction. We argue that open-ended self-modification presupposes such a kernel, that the kernel is individuated functionally rather than materially, so that total self-modifiability is coherent diachronically but not synchronically, and that at closure the system's full autonomy and its governability by a designer cannot be jointly satisfied.