X is usually taken as the symbol of the unknown in modern thought. If a man wishes to discover an unknown figure or fact, he begins by positing ‘X’ as the object of his enquiry and then he proceeds to argue in such a way as to reveal the nature of that unknown. In the ‘argument’ of the spiritual life the process is largely reversed. Having begun with a ‘clear idea’ of God, derived partly from reason and partly from faith, the Christian gradually ascends the holy mount until this sun disappears behind the luminous cloud and he finds himself surrounded thickly on all sides by the Unknown. It is in many ways the conclusion of his search.

But having become aware that he is enveloped in this cloud of unknowing, the Christian may well take the opportunity to run over in his mind the way he came into this place and the means he had taken to ensure that he should ascend at every pace.