The same conclusion would seem to follow from the close connection that exists between each pleasure and the exercise of faculty which it completes. For the exercise is increased by its proper pleasure; e.g. people are more likely to understand any matter, and to go to the bottom of it, if the exercise is pleasant to them. Thus, those who delight in geometry become geometricians, and understand all the propositions better than others; and similarly, those who are fond of music, or of architecture, or of anything else, make progress in that kind of work, because they delight in it. The pleasures, then, help to increase the exercise; but that which helps to increase it must be closely connected with it: but when things are specifically different from one another, the things that are closely connected with them must also be specifically different.