Answer:
In this situation the therapist was trying to determine the etiology of Buck's psychological problems.
Explanation:
The word etiology refers to the study of the causes in general, and in biology, of diseases, for this reason is a term that observes a great use of medical as well as philosophical contexts. Since Buck's therapist wants to begin an assessment to enter the onset of Buck's problems, which caused those problems, we can conclude that the therapist wants to determine the aetiology of the psychological problems of Buck and thus be able to create a treatment that solves these problems.