 Stein further distinguishes between “species” (understood as Aquinas’ “forms” which are permanent and unalterable categories (2000c: 151[173]), and what she calls, following Husserl, “types”. Types can vary within the limits defined by the species. A single person can exemplify many types, e.g., by age, social status, etc. Stein maintains that each entity—from a plant to an animal or human being—has an inner “form” (Gestalt) that determines it to become the thing it is—just as individual seeds become beech trees or fir trees (2000c: 32[130]).