With your eyes you can only understand a thing by its appearance... With your ears you understand by noise or sound; with your nose by stench or scent; with your taste whether it is sour or sweet, salt or fresh, bitter or pleasant; with your touch whether it is hot or cold, hard or soft, blunt or sharp.
But God and spiritual things have none of these varied attributes. Therefore leave all outer knowledge gained through the senses...
For even if a man is deeply versed in the understanding and knowledge of all spiritual things ever created, he can never by such understanding come to know an uncreated spiritual thing ... which is none else than God! (p. 144-145)