3. But, as is commonly said, no one can comprehend spiritual, that is, theological matters because they are supernatural. Spiritual truths, however, are as capable of being comprehended as natural truths; and although the comprehension of them may not be clear, still when they are heard they fall so far within the perception of the hearer that he can discern whether they are truths or not; and this is especially the case with those who are affected by truths. This has been granted me to know from much experience. It has been granted me to converse with those who are ignorant, obscure and dull; and also with those who had been born within the Church and who had heard something about the Lord, about faith and about charity, yet who were immersed in falsities and in evils. It was also granted me to speak with them concerning arcana* of wisdom; and they comprehended them all and acknowledged their truth; but they were then in the light of understanding which every man possesses, and at the same time in the glory of being intelligent. These things however occurred in my intercourse with spirits.
Many who were present with me were convinced by these experiences that spiritual things are as capable of being comprehended as natural things, that is, when they are heard or read; but they are comprehended with difficulty by the man himself when he is thinking from himself. The reason that spiritual things can be comprehended is, because man as to his understanding is capable of being elevated into the light of heaven, in which light appear none but spiritual things which are truths of faith: for the light of heaven is spiritual light. * Arcanum (plur. arcana) what is shut up, enclosed, from arceo to shut up, and arca, an ark, chest or box. Usual connotation, hidden things.