This was a result of freedom that the Professor had never bargained for. He could not understand it, 'because,' he argued, 'if people were to reason in that way, morality would at once cease to be possible.' But he had seen so much of the world lately, that he soon recovered himself, and recollecting that immorality was only ignorance, he began to show Virginia where her error lay---her one remaining error. 'I perceive,' he said, 'that you are ignorant of one of the greatest triumphs of exact thought--the distinction it has established between the lower and the higher pleasures. Philosophers, who have thought the whole thing over in their studies, have become sure that as soon as the latter are presented to men they will at once leave all and follow them.' 'They must be very nice pleasures,' said Virginia, 'if they would make me leave kissing you for the sake of them.' 'They _are_ nice,' said the Professor. 'They are the pleasures of the imagination, the intellect, and the glorious apprehension of truth. Compared with these, kissing me would be quite insipid. Remain here for a moment, whilst I go to fetch something, and you shall then begin to taste them.' In a few moments Paul came back again, and found Virginia in a state of intense expectancy. 'Now--,' he exclaimed triumphantly. 'Now--,' exclaimed Virginia, with a beating heart. The Professor put his hand in his pocket, and drew slowly forth from it an object which Virginia knew well. It reminded her of the most innocent period of her life; but she hated the very sight of it none the less. It was a Colenso's Arithmetic. 'Come,' said the Professor, 'no truths are so pure and necessary as those of mathematics; you shall at once begin the glorious apprehension of them.' 'Oh, Paul,' cried Virginia, in an agony, 'but I really don't care for truth at all; and you know that when I broke your tin box open and read your private letters in my search for it, you were very angry with me.' 'Ah!' said Paul, holding up his finger, 'but those were not necessary truths. Truths about human action and character are not necessary truths; therefore men of science care nothing about them, and they have no place in scientific systems of ethics. Pure truths are of a very different character; and, however much you may misunderstand your own inclinations, you can really care for nothing so much as doing a few sums. I will set you some very easy ones to begin with, and you shall do them by yourself, whilst I magnify in the next room the parasites of the missing link.' Virginia saw that there was no help for it. She did her sums by herself the whole morning, which, as at school she had been very good at arithmetic, was not a hard task for her, and Paul magnified parasites in the next room, and prepared slides for his microscope.