All over the world thousands upon thousands of men and women pass their whole lives denouncing, instructing, commanding, cajoling, imploring their fellows. With what results? One finds it rather hard to say. Most propagandists do their work in the dark, draw bows at a venture. They write; but they don’t know how far they will succeed in influencing their readers, nor what are the best means for influencing them, nor how long their influence will last. There is, as yet, no science of propaganda.

This fact may seem the more surprising when we consider that there is something not…