I read, interpreted and answered your comment much too hastily, and now I feel foolish. Please accept my sincerest apologies. In my defense, I can only point to the large number of posts that are frustratingly missing the point, and to the fact that I am regrettably not the most patient of persons.

Let me try again...

My response should have been something like "my question is less focused on the metaphysics, and more focused on what I think is an issue of logic, so I am happy to stick to the level of analysis of a university hospital textbook". It seems to be the case that people are attempting to partition the phenomenon of addiction into psychological vs physiological addiction. My issue is twofold:

1. I know of no substance that is well-established as being addictive that does not produce both (1) a physiological response at the time of consumption/engagement and (2) an unpleasant physiological withdrawal symptom of some kind. This notably includes drugs that are popularly described as being purely psychologically addictive, such as cannabis.

2. The psychological (i.e. cognitive and behavioral) patterns that we associate with addiction are driven, in a fairly direct manner, by the physiological responses to the presence and absence of the drug. Addicts return to drugs both to avoid physiological withdrawal symptoms and to pursue pleasurable physiological effects.

Together, these suggest a psychological effect of the drug that mediated by physiology. In all cases, the physiological phenomena are necessary. I am generally quite sensitive to arguments of emergence at a particular scale, but I don't see the necessity for it here. Can you be more precise? The closest you come to providing an example has to do with a "reminder of who you are and what you desire". I am also not-insensitive to higher-order explanations for behavior, including some from the psychoanalytical tradition, but I don't think these negate the causal chain outlined in point #2. Therefore, I don't see how psychological addiction can exist separately from physiology, except perhaps in the trivial case of categorizing psychology as a subset of or emergence from physiology. Certainly, I think, one does not encounter "psychological addiction" without also encountering its physiological counterpart, rendering the ontological distinction questionable. It is further made questionable by the prima facie dualist argument that subtends the psychological-vs-physiological distinction. Certainly, if this is not a dualist position, the argument is not immediately obvious to me, and I would be interested in hearing it.

Moreover, if you'll allow me to stray from the purely logical argument surrounding biology and psychology, my sense is that this dichotomy between physiological and psychological addiction is in large part a semantic game that serves to advance a certain political discourse. Invariably, it serves to argue that cannabis isn't "really" addictive by arguing that is withdrawal is qualitatively very different from that of, say, heroin. To this I can only say, "of course it is!" Nobody is really arguing that cannabis is as dangerous as heroin! But this is indeed the argument of scale; I might be convinced that the severity of cannabis' toxicity, intoxication and withdrawal is minor enough to warrant the drug's legality, but I still contend that for those who are addicted to cannabis, the same commingling of physiological state and behavior is at play.

And in case it needs to be said, of course the difference in degree that separates cannabis from heroin (and other "hard" drugs) is large enough to place the two in qualitatively different categories. Again, my point is that despite this, both produce their addictions in similar ways (roughly: the dopaminergic circuit), as is supported by the scientific literature.

(Edits made for clarity.)