1387. I have spoken on several occasions about perception to those in the next life who, while they lived in the world, imagined that they had the ability to see into and understand all things. I told them that angels perceive that they think and speak, will and act, from the Lord; but they were still unable to envisage what perception was, for they imagined that if all things flowed in from Him in that way they would be bereft of all life. They would be bereft of it because they would not think anything from themselves or from their proprium - in which activity they made life consist - and so it would be another who did the thinking and not they themselves, so that they would be organs without any life in them. They were told however that so far as life is concerned the difference between having perception and not having it is like the difference between darkness and light, and that people first begin to feel alive when they are receiving such perception, for in that case they live from the Lord yet also have a proprium, which is imparted to them together with every happiness and delight. They were also shown from much experience what perception really was, during which time they acknowledged the existence of it. But after a while they again had no knowledge of it, and doubted and denied its existence. This made clear how difficult it is for man to grasp what perception is.