God has given our bodies these powers, and they are good. Purity is the proper control of these pleasures; impurity is the selfish attempt to enjoy these pleasures, when we have no right to them. So until a person is married he is bound to control himself very strictly in his thoughts, in his words, and in his actions.

4. Thoughts, words and actions
I'll speak about these, because temptations often worry boys.

(a) Thoughts. Sometimes it might happen that you suddenly realise that there is a wrong thought, an impure thought, in your mind. If you couldn't help it coming into your mind, you are not to be blamed, so far. But as soon as you realise that it is there, you must do your best to put it out. And the best way to do that is just to think of something else (of engines, stamps, football, or whatever your hobby may be) and worry no more about it. And the same goes for pictures you might see in books or at the ' pictures'. Just turn away from them, quite calmly. Remember, there is all the difference in the world between a temptation and a sin. If you try to put the thoughts out of your mind, you have done good. But if you are careless or slow in putting them out, that would be a venial sin; and if you keep them in your mind on purpose to enjoy wrong pleasures, that would be a mortal sin.

(b) Words. If there is need, of course it is all right to talk about these things; and if ever there is need, you ought to know that we usually call these parts of the body the 'private parts'. So if ever you want to know anything, ask me, or your mother, or if you want to know whether a thing is right or wrong, ask the priest in confession. It will probably happen that as you get older, you will feel shy to ask. But if you have a worry or a difficulty, you should overcome this shyness and get the difficulty cleared up.

But you must not talk of these things to the other boys at school. That would be immodest talk, and sinful, and it might easily lead to much more serious sins.