What is the difference between certainty and conviction? Conviction is indirect and belongs to the mind, being the result of purely mental processes such as argument. But certainty, being always direct, can be the result of sensory perception; hearing or touch or sight can give certainty. But in it’s spiritual sense, when it has for object the Transcendent, certainty is the result of Heart-knowledge. Failing this knowledge in its fullest sense, those elements which are nearest the Heart at the summit of the soul must also be considered as faculties of direct perception, albeit in a fragmentary way; and through the light which these faculties of intuition receive in virtue of the transparency of the barrier, a soul may claim to be possessed of a faith which is no less than certainty.
– Martin Lings