The rule seems to be that there are no absolutes, that what is rare is prized. Thus, in times of relative affluence, thin models become dominant.

You have to believe in a placebo or it won't work, but if it works, it's obviously working in some indirect way, through feedback in the immune system, let us say, or in the willpower of the patient to take a more strenuous exercise in their own therapy.

A placebo is a phony cure that works. This is very hard for the medical profession to get their teeth around because they hate placebos, but scientifically, placebos work in about 30% of cases that are psychogenic diseases.

Charles Jencks Quotes