首楞嚴義疏注經 8.510

8.510

獄、鬼二趣，業火燒畢，情想乾枯，今為畜生酬償餘業，故云旁為。妄想故有，覺性元無，猶如圓影，眚病故見。

In the two destinies of hell and ghosts, the karmic fires having burned out, emotion and thought dry up; now they become animals to pay back their remaining karma, which is why it says 'laterally becoming.' They exist because of false thinking, but in the nature of awareness fundamentally do not exist, just like a circular halo seen because of an eye disease.