Of all the temperaments a child can be born with, Locke considers sluggishness the worst. It is both the most destructive to a child's future, and also the hardest to cure. By "sluggishness" Locke means a general lack of regard for anything. A sluggish person is indifferent to his fate, and does not try hard to accomplish anything. Locke is careful to warn parents to distinguish between a legitimate sluggishness (an indifference to absolutely everything) and a more narrow listlessness during learning. The way to determine which of these a child suffers from, is to watch the child at play. If he is energetic while playing then it is the latter; is he is listless even while playing then it is the former.
If it is the latter that a child is suffering from, then Locke suggests reasoning with the child, and pointing out how much more time he would have for play if he only applied himself more industriously to his studies. If this does not work then an attempt should be made to shame the child out of his behavior. If there is still no effect then more drastic measures must be taken. The must be forced to play a certain number of hours a day, and watched to make sure that he keeps at his play consistently. Eventually, Locke predicts, he will become so sick of playing that he will want to learn.
If, on the other hand, the child suffers from a pervasive and all-embracing sluggishness, then an entirely new sort of tact must be taken. In this case, the parent must find something that the child likes (such as sweets) and use this to motivate him. This sort of motivation is permissible here, and here alone, because excess of appetite is not a concern at this point; it is appetite that we are trying to stir up. If this does not work, then the parent can try to stir up the child's vigor by setting him to some constant physical labor. Through the labor, the child will get in the habit of engaging in vigorous activity, even if it is not the activity you would prefer him to apply himself to vigorously. The reason that physical labor is preferable to study for this exercise, is that in the case of physical labor one can actually observe whether or not the child is performing this task idly or with industry (whereas in the case of study, it is harder to tell).
Locke next considers what to do if your child is overly fond of some one particular toy. As in the case of the sluggish learner, he suggests that the parents make it a duty for the child to play with that toy for a certain number of hours a day. Learning should be set as the reward for that duty. At this point Lock takes the opportunity to mention some other thoughts on toys. A child should only be allowed to play with one toy at a time, so that he does not become careless about his belongings. And while he should have a nice variety of things to play with, none of these should be bought. Instead he should be content with things he finds around the house or makes himself. This way he will not grow acquisitive and feel that he always needs more.
The final inclination that Locke considers before concluding the section on moral education is dishonesty. Lying, Locke tells us, should always be spoken of with the utmost detestation. Excuses should not be indulged either, because they lead to lying. In order to make a child love the truth, he should never be punished if he readily confesses some crime. He should learn that honesty never leads to inconvenience.
Here again, we find Locke discounting the possibility of a real natural diversity in personalities. Locke's theory that by forcing a child to play for a certain number of hours a day he will grow sick of playing and come to crave learning is not necessarily true. We can imagine certain types of people who would be perfectly content to be forced to play all day, and would never come to crave learning as a relief from this activity. For instance, imagine a child who lives for games of pretend. (Perhaps this child is destined to be a novelist or a playwright or an actress.) This child has a brilliant and inexhaustible imagination, but she absolutely hates mathematics, geography, Latin and all the other intellectual pursuits that make up academic learning at this young age. Her mind is just not suited to these pursuits. If you force her to play all day, she will be perfectly happy. She will create elaborate games of pretend, with layers of plots and subplots. Never once will she think fondly of giving up her game for a lesson in arithmetic.