TA therapists disagree about the distinctions between structural and functional analysis. Structural commonly refers to (1) historical developments, (2) intrapsychic or internal transactions, (3) the internal organization of such components or some combination of the above. Berne's own progression from descriptive (functional) analysis to structural analysis parallels his increasing use of the therapy group for work he had previously conducted in one to one psychoanalytic therapy. Concepts from general systems theory may be employed to clarify the theoretical distinctions between structural and functional analysis as well as their practical implications for psychotherapy and TA.