In particular: "Can reasoning itself have causal or motivational force, for example in countering affect or impulse, or must it arouse/recruit affect in order to have such influence?" Seems to me when we reflect on our motivations we can encounter many things: desires, thoughts, emotions, confusion, imprints from experience, etc. Most likely there's not a black-&-white answer here. Perhaps only a subset of our motivations can be articulated through reasoning? Could reasoning actually be "self-fulfilling" in some contexts? The question: "why did you do that" might elicit reasons as a response for a particular act but can reason always explain motivation - or only rationalize it?
Article Reasoning, Cognitive Control, and Moral Intuition