You must know that if a person, who has attained a certain degree of perfection, wishes to impart to others, either orally or in writing, any portion of the knowledge which he has acquired of these subjects, he is utterly unable to be as systematic and explicit as he could be in a science of which the method is well known. The same difficulties which he encountered when investigating the subject for himself will attend him when endeavouring to instruct others: viz., at one time the explanation will appear lucid, at another time, obscure: this property of the subject appears to remain the same both to the advanced scholar and to the beginner. For this reason, great theological scholars gave instruction in all such matters only by means of metaphors and allegories.