Every time you make a choice you are turning the central part of you, the part of you that chooses, into something a little different than it was bef… - C. S. Lewis

"Alas," said Aslan, shaking his head. "It will. Things always work according to their nature. She has won her heart's desire; she has unwearying strength and endless days like a goddess. But length of days with an evil heart is only length of misery and already she begins to know it. All get what they want; they do not always like it."

Above all, do not attempt to use science (I mean, the real sciences) as a defence against Christianity. They will positively encourage him to think about realities he can’t touch and see.

The sins of the flesh are bad, but they are the least bad of all sins. All the worst pleasures are purely spiritual: the pleasure of putting other people in the wrong, of bossing and patronising and spoiling sport, and back-biting; the pleasures of power, of hatred. For there are two things inside me, competing with the human self which I must try to become. They are the Animal self, and the Diabolical self. The Diabolical self is the worse of the two. That is why a cold, self-righteous prig who goes regularly to church may be far nearer to hell than a prostitute. But, of course, it is better to be neither.