4613. How strongly principles operate, may be evident merely from this: if any one believes that the food in which he has delighted is injurious to him, he then, by virtue of that principle, abstains from that food, and, at length, turns away from it in dislike - if he only adopt that persuasion, or be in it from some physician whom he supposes to know. It is thus in many other cases: so that principles subdue affections. Hence it may be evident, of how great importance it is to be acquainted with the knowledges of truth, and to believe that what is here stated is true.