Any adjunction produces an epireflection in a canonical way, provided there exists a prefactorization system which factorizes all of its unit morphisms through epimorphisms. The stable units property, for the so obtained epireflections, is thereafter equivalently restated in such a manner it is easily recognizable in the examples. Furthermore, having stable units, there is a strong but quite si...

We explored whether rhesus monkeys (Macaca mulatta) share one important feature of human essentialist reasoning: the capacity to track category membership across radical featural transformations. Specifically, we examined whether monkeys--like children (Keil, 1989)--expect a transformed object to have the internal properties of its original category. In two experiments, monkeys watched as an ex...

The notion of a subtractive category, recently introduced by the author, is a “categorical version” of the notion of a (pointed) subtractive variety of universal algebras, due to A.Ursini. We show that a subtractive variety C, whose theory contains a unique constant, is abelian (i.e. C is the variety of modules over a fixed ring), if and only if the dual category Cop of C, is subtractive. More ...