Contemplative life hath three parts. The first consisteth in knowing God, and of spiritual things gotten by reason and discourse, by teaching of men, and by study in holy Scripture, without spiritual gust, or affection, or inward relish felt by them; for they have it not by the special gift of the Holy Ghost, as persons truly spiritual have their knowledge, which, therefore, is very tasteful to them in their interior. (John Climacus)

Can I know God without spiritual affection, and only through reason and discourse?

I can know of God. I can be acquainted with God. I can have an intellectual understanding of God.

John was writing in Greek, but I do not have his original Greek. I expect his "knowing" is a form of either γνῶσις (gnosis) or ἐπιστήμη (episteme). Using episteme would further strengthen the distinction he seems to make.

For anyone familiar with Aristotle, episteme is to know as we know geometry. It is to know something that does not change, a knowledge that can be demonstrated, it is a knowledge where theory and practice are in exact accord. It is also a knowledge that is explicit and without mystery.

Objects beyond explicit measure are not well-matched to episteme. Such objects may be experienced, but are beyond precise definition. The infinite can be experienced, but cannot be measured. This experiential knowing or gnosis is most appropriate for knowing God.