Aristotle on Psychic Subjecthood and Explanation

In recent years, vigorous debate has emerged around a question central to Aristotelian psychology and metaphysics. This question is often framed in ontological terms, and concerns the sorts of causal roles played by the Aristotelian souls of various living organisms. More precisely, it asks whether such souls are ever capable of immediately or non-derivatively underlying the sorts of states and transitions involved in intuitively psychological phenomena such as perception, emotion, or thought, or whether these states and transitions must instead belong directly or non-derivatively to ensouled living things such as human beings, horses, and dogs. When Socrates builds a house, Bucephalus sees a certain shade of yellow, or Fido gets angry at the mailman, in other words, will these ostensibly cognitive activities ever involve instances of knowledge, states of awareness, or causally relevant events that belong directly to their individual souls in the way that a certain weight belongs directly to the materials making up a bronze sphere, or in the manner that various phenomenal experiences are often held to be immediately present in something akin to a Cartesian mind? Or will such cognitive activities instead be fully explicable in terms of bodily states that are ultimately explained by, while nevertheless failing to directly belong to, the Aristotelian souls that make them possible? According to the currently dominant line of reasoning, Aristotle's mature thoughts on the soul rule out the possibility of such psychic subjecthood. In the De Anima, the argument typically goes, the soul is defined as the "substantial form" or "first actuality" of a certain sort of living body, and however we are to interpret this characterization, it is clear that it does not require the introduction of some additional entity that might stand as an independent subject for "mental" states and events. Instead, we are told, the claim that a given organism has a certain type of soul indicates something about how