The conventional wisdom or received opinion is the body of ideas or explanations generally accepted by the public and/or by experts in a field.
Galbraith specifically prepended "The" to the phrase to emphasize its uniqueness, and sharpened its meaning to narrow it to those commonplace beliefs that are also acceptable and comfortable to society, thus enhancing their ability to resist facts that might diminish them.
He repeatedly referred to it throughout the text of The Affluent Society, invoking it to explain the high degree of resistance in academic economics to new ideas.
More narrowly, the conventional wisdom in science and engineering once was that a man would suffer lethal injuries if he experienced more than eighteen g-forces in an aerospace vehicle, but it is so no longer.
Evidence-based medicine is a deliberate effort to acknowledge expert opinion (conventional wisdom) and how it coexists with scientific data.