Lewis’ argument from desire posits a certain degree of ignorance as to how the object of desire fulfills that Sehnsucht (literally meaning mind-search, a deep and mysterious longing for something, usually lasting).

1. Every natural, innate desire corresponds to some real object that can satisfy that desire.
2. But there exists a desire space, time, or anything can satisfy. This desire is not the difference of degree of natural desire but a different kind.
3. Therefore, There must exist something more than these natural [natural], which can satisfy this desire.

He ascribes certain subjective pleasures to an object, which rests at an epistemic distance.  There is a concrete/abstract dilemma, which keeps us from knowing a thing completely.  We can know about it; we can experience it.  Both cannot be done simultaneously and each has its limits when isolated.  This epistemic problem, or the lapse in knowledge in illicit pleasure, is due to a separation of the subject from the object[1].  Lewis roots the epistemic dilemmas, the loss of concrete thought, in a long process of separation that begins in the fall.