“If you don’t vent the drain pipe like this, sewage gases will seep up through the water in the toilet, and the house will stink of shit.” In the trades, a master offers his apprentice good reasons for acting in one way rather than another, the better to realize ends the goodness of which is readily apparent. The master has no need for a psychology of persuasion that will make the apprentice compliant to whatever purposes the master might dream up; those purposes are given and determinate. He does the same work as the apprentice, only better.
