959. I awoke in the night from my sleep, and heard spirits about me who desired to ambush me in my sleep, yet presently dozing I had a sad dream. But having awaked, punishing spirits were suddenly present-at which I wondered-and miserably punished the spirits who had ambushed me in my sleep. They induced on them as it were bodies-visible ones-and bodily senses, and thus tortured them by violent collisions of the parts to and fro, with pains induced by resistance. The punishers would have killed them if they could, so that they used the most extreme violence. Those guilty were for the most part sirens (concerning whom see n. 831). The punishment lasted a long time, and extended around me to many troops, and to my astonishment all those who had ambushed me were found, though they wanted to hide themselves. Being sirens, they tried with many arts to elude the penalty, but could not. Now they sought to withdraw into interior nature, now to induce the belief that they were others, now to transfer the punishment to others by a transference of ideas, now they counterfeited infants who would thus be tortured, now good spirits, now angels, besides making use of many other artifices, but all in vain. I was surprised that they should be so grievously punished, but perceived that the crime is enormous from the necessity of man's being able to sleep in safety, without which the human race would perish; so that it is of necessity that there should be so great a penalty. I perceived that the same takes place around other men whom they attempt to assail insidiously in their sleep, although the men know nothing about it. For one to whom it is not given to speak with spirits and to be with them by inner sense, can hear nothing of the kind, still less see it, when yet the same things happen with all. The Lord guards man with most especial care during his sleep.