"Although there are passages in the scriptural writings of the Hindus which apparently refer to the retrogression of the human soul into animal nature, still such passages do not necessarily mean that the souls will be obliged to take animal bodies. They may live like animals even when they have human bodies, as we may find among us many people like cats and dogs and snakes in human form and they are often more vicious than natural cats, dogs or snakes. They are reaping their own Karma and manifesting their animal nature, though physically they look like human beings. This kind of retrogression is possible for one who after reaching the human plane goes backward on account of wicked thoughts and deeds on the animal plane. (V. Theory of Transmigration)"