Twenty units, in order

Before any system, the prior question: what makes something psychotherapy rather than advice, friendship, education or medicine — and how can approaches with incompatible premises be compared at all?

From the moral treatment movement through Freud, behaviourism, the humanistic reaction, the cognitive revolution and the evidence-based practice movement — and the parts of that history the field has been slow to tell.

Empirically supported treatments, evidence-based practice, and practice-based evidence — three related ideas that are frequently confused, and the methodological machinery underneath them.

The dodo bird verdict, the contextual model, therapist effects, deterioration, and routine outcome monitoring — the findings that unsettle every school equally.

Unconscious motivation, defense, transference, resistance — and the four psychologies the tradition became.

Adler, Horney and Sullivan replaced drive with relationship; Malan, Luborsky, Davanloo and their successors made the result brief enough to test.

Death, freedom, isolation and meaninglessness — and the clinical question of when anxiety is the correct response.

Six conditions, stated as necessary and sufficient, tested for sixty years, and falsified in a way that vindicated most of what they contained.

Gestalt supplied the methods; emotion-focused therapy tested them and found out which parts work.

Sullivan’s interpersonal field, the circumplex and complementarity, Benjamin’s reconstructive therapy, and IPT — the most deliverable evidence-based treatment in the world.

Two-factor theory, safety behaviours, and the shift from habituation to inhibitory learning — plus the therapist avoidance that keeps this treatment from patients who need it.

Functional analysis, contingencies, behavioural activation — and the finding that the simplest component of cognitive therapy carried much of its effect.

Beck and Ellis, automatic thoughts and core beliefs, collaborative empiricism — and the mediation evidence that has never quite arrived.

ACT, DBT, MBCT and compassion-focused therapy — behavioural at the root, contextual in method, and the answer to what cognitive therapy could not reach.

Circular causality, structure, attempted solutions, and the feminist critique that reshaped the field.

Minority stress, cultural humility, the WEIRD problem, and the single most damaging error available to a therapist.

The two-continua model, well-being therapy, and a brief therapy that declines to discuss the problem at all.

Four routes to integration, the transtheoretical model, and the discipline that separates integration from drift.

Set and setting, preparation and integration, and a regulatory decision that turned on methodology rather than on enthusiasm.

Where the systems genuinely disagree, where they merely use different words, what the field looks like in twenty years, and what your own model of change actually is.