Titus 1:15–16

To the pure, all things are pure; but to those who are defiled and unbe­liev­ing, noth­ing is pure, but both their mind and their con­science are defiled. They pro­fess to know God, but by their deeds they deny Him, being detestable and dis­obe­di­ent and worth­less for any good deed.

I won­der if Lewis was not con­sid­er­ing this pas­sage when he wrote Book 3: Chap­ter 8 of A Pil­grim’s Regress, “Par­rot Dis­ease”. ‘Are you a liar or only a fool, that you see no dif­fer­ence between that which Nature casts out as refuse and that which she stores up as food?’

Every day a jailor brought the pris­on­ers their food, and as he laid down the dish­es he would say a word to them. If their meal was flesh he would remind them that they were eat­ing corpses, or give them some account of the slaugh­ter­ing: or, if it was the inwards of some beast, he would read them a lec­ture in anato­my and show the like­ness of the mess to the same parts in themselves—which was the more eas­i­ly done because the giant’s eyes were always star­ing into the dun­geon at din­ner time. Or if the meal were eggs he would recall to them that they were eat­ing the enstru­um of a ver­minous fowl, and crack a few jokes with the female pris­on­ers. So he went on day by day. Then I dreamed that one day there was noth­ing but milk for them, and the jailor said as he put down the pipkin:

‘Our rela­tions with the cow are not delicate—as you can eas­i­ly see if you imag­ine eat­ing any of her oth­er secre­tions.’ Now John had been in the pit a short­er time than any of the oth­ers: and at these words some­thing seemed to snap in his head and he gave a great sigh and sud­den­ly spoke out in a loud, clear voice:

‘Thank heav­en! Now at last I know that you are talk­ing nonsense.’

‘What do you mean?’ said the jailor, wheel­ing round upon him.

‘You are try­ing to pre­tend that unlike things are like. You are try­ing to make us think that milk is the same sort of thing as sweat or dung.’

‘And pray, what dif­fer­ence is there except by custom?’

‘Are you a liar or only a fool, that you see no dif­fer­ence between that which Nature casts out as refuse and that which she stores up as food?’

‘So Nature is a per­son, then, with pur­pos­es and con­scious­ness,’ said the jailor with a sneer. ‘In fact, a Land­la­dy. No doubt it com­forts you to imag­ine you can believe that sort of thing;’ and he turned to leave the prison with his nose in the air.

‘I know noth­ing about that,’ shout­ed John after him. ‘I am talk­ing of what hap­pens. Milk does feed calves and dung does not.’

‘Look here,’ cried the jailor, com­ing back, ‘we have had enough of this. It is high trea­son and I shall bring you before the Mas­ter.’ Then he jerked John up by his chain and began to drag him towards the door; but John as he was being dragged, cried out to the oth­ers, ‘Can’t you see it’s all a cheat?’ Then the jailor struck him in the teeth so hard that his mouth was filled with blood and he became unable to speak: and while he was silent the jailor addressed the pris­on­ers and said:

‘You see he is try­ing to argue. Now tell me, some­one, what is argument?’

There was a con­fused murmur.

‘Come, come,’ said the jailor. ‘You must know your cat­e­chisms by now. You, there’ (and he point­ed to a pris­on­er lit­tle old­er than a boy whose name was Mas­ter Par­rot), ‘what is argument?’

‘Argu­ment,’ said Mas­ter Par­rot, ‘is the attempt­ed ratio­nal­iza­tion of the arguer’s desires.’

‘Very good,’ replied the jailor, ‘but you should turn out your toes and put your hands behind your back. That is bet­ter. Now: what is the prop­er answer to an argu­ment prov­ing the exis­tence of the Landlord?’

‘The prop­er answer is, “You say that because you are a Steward.”’

‘Good boy. But hold your head up. That’s right. And what is the answer to an argu­ment prov­ing that Mr. Phally’s songs are just as brown as Mr. Halfways’?’

‘There are two only gen­er­al­ly nec­es­sary to damna­tion,’ said Mas­ter Par­rot. ‘The first is, “You say that because you are a Puri­tan­ian,” and the sec­ond is, “You say that because you are a
sensualist.”’

‘Good. Now just one more. What is the answer to an argu­ment turn­ing on the belief that two and two make four?’

‘The answer is, “You say that because you are a mathematician.”’

‘You are a very good boy,’ said the jailor. ‘And when I come back I shall bring you some­thing nice. And now for you,’ he added, giv­ing John a kick and open­ing the grating.