Erratum

C. S. Lewis, in his essay The Weight of Glory and in a letter dated 23 December 1950, quotes Matthew Arnold, in order to take up his idea but develop it further to draw an opposite conclusion:

Here is the quotation from the letter:

At one time I was much impressed by Arnold's line `Nor does the being hungry prove that we have bread.' But surely tho' it doesn't prove that one particular man will get food, it does prove that there is such a thing as food! i.e. if we were a species that didn't normally eat, weren't designed to eat, wd. we feel hungry?

I've looked considerably, however, and cannot find that line in Arnold's works.

What I do find is this, from Arnold's Empedocles on Etna:

Fools! That in man’s brief term

He cannot all things view,

Affords no ground to affirm

That there are gods who do;

Nor does being weary prove that he has where to rest.

Empedocles argues that our ignorance does not entail the existence of an omniscience and that the existence of desire does not entail its satisfaction.

C. S. Lewis's argument, however, is essentially that the quality of ignorance presupposes the existence of knowledge and the quality of tiredness presupposes the existence of rest. The question of the existence of knowledge and rest is separate from the question of their attainment.