The early days of the emerging discipline of psychology were inevitably rigidly dogmatic. Clinicians belonged to well-demarcated schools and practiced in strict accordance with canons of writings by "masters" such as Freud, or Jung, or Adler, or Skinner. Psychology was less a science than an ideology or an art form. Freud's work, for instance, though incredibly insightful, is closer to literature and cultural studies than to proper, evidence-based, medicine.

Not so nowadays. Mental health practitioners freely borrow tools and techniques from a myriad therapeutic systems. They refuse to be labeled and boxed in. The only principle that guides modern therapists is "what works" - the effectiveness of treatment modalities, not their intellectual provenance. The therapy, insists these eclecticists, should be tailored to the patient, not the other way around.

This sounds self-evident but as Lazarus pointed out in a series of articles in the 1970s, it is nothing less than revolutionary. The therapist today is free to match techniques from any number of schools to presenting problems without committing himself to the theoretical apparatus (or baggage) that is associated with them. She can use psychoanalysis or behavioral methods while rejecting Freud's ideas and Skinner's theory, for instance.

Lazarus proposed that the appraisal of the efficacy and applicability of a treatment modality should be based on six data: BASIC IB (Behavior, Affect, Sensation, Imagery, Cognition, Interpersonal Relationships, and Biology). What are the patient's dysfunctional behavior patterns? How is her sensorium? In what ways does her imagery connect with her problems, presenting symptoms, and signs? Does he suffer from cognitive deficits and distortions? What is the extent and quality of the patient's interpersonal relationships? Does the subject suffer from any medical, genetic, or neurological problems that may affect his or her conduct and functioning?

Once the answers to these questions are collated, the therapist should judge which treatment options are likely to yield the fastest and most durable outcomes, based on empirical data. As Beutler and Chalkin noted in a groundbreaking article in 1990, therapists no longer harbor delusions of omnipotence. Whether a course of therapy succeeds or not depends on numerous factors such as the therapist's and the patient's personalities and past histories and the interactions between the various techniques used.

So what's the use of theorizing in psychology? Why not simply revert to trial and error and see what works?

Beutler, a staunch supporter and promoter of eclecticism, provides the answer:

Psychological theories of personality allow us to be more selective. They provide guidelines as to which treatment modalities we should consider in any given situation and for any given patient. Without these intellectual edifices we would be lost in a sea of "everything goes". In other words, psychological theories are organizing principles. They provide the practitioner with selection rules and criteria that he or she would do well to apply if they don't want to drown in a sea of ill-delineated treatment options.