Desire, as you will see by the terms of the law of sale, is merely interest intensified. Desire is the main spring of action. It is the real force of every motive. Contradictory as it may seem at first sight, people always do what they want to do even when they act most reluctantly. Their action is inspired by a desire to escape what they believe to be the certain penalty of inaction or of contrary action. The boy who slowly approaches his father to receive a promised whipping, does so because he wants to. And he wants to because he knows he will be whipped so much harder if he runs away. Desire is, therefore, the great citadel toward which all of the campaign of the persuader must be directed. Given a powerful enough desire, decision and action follow as a matter of course. Psychologists have determined that imagination is the most powerful mental stimulus to desire. Imagination presents to the mind, as it were, a more or less vivid mental picture of the individual enjoying the gratification of his desire--be it physical, intellectual, or spiritual. The longer this picture remains in the mind, the more vivid it becomes, the more it crowds all other thoughts and feelings from the mind, the more powerful and irresistible becomes the desire. It is the task of the persuader, therefore, to stimulate the imagination to the painting of such mental pictures. This we well know, but what we wish to know further is what are the most powerful desires in the particular human mind with which we are dealing. Obviously, the automobile salesman who vividly pictures to the timid person the thrills of speeding around curves would be as far wrong as if he were picturing the sedate, quiet luxury of his car to a speed maniac. What he wants to know and what we all want to know in substance is how to tell, at a glance, which is the timid, sedate person and which the speed maniac. DECISION AND ACTION