When God through his life-giving breath created the soul deiform and intellective, He did not implant in it anger and desire that are animal-like. But He did endow it with a power of longing and aspiration, as well as with a courage responsive to divine love. Similarly, when God formed the body He did not originally implant in it instinctual anger and desire. If was only afterwards, through the fall, that it was invested with these characteristics that have rendered it mortal, corruptible and animal-like. For the body, even though susceptive of corruption, was created, as theologians will tell us, free from corruption, and that is how it will be resurrected.
In the same way the soul when originally created was dispassionate. But soul and body have both been defiled, commingled as they are through the natural law of mutual interpenetration and exchange. The soul has acquired the qualities of the passions, or rather, of the demons; and the body, passing under the sway of corruption because of its fallen state, has become akin to instinct-driven animals. The powers of the body and soul have merged together and have produced a single animal, driven impulsively and mindlessly by anger and desire. That is how man has sunk to the level of animals, as Scripture testifies, and has become like them in every respect (cf. Psalm 49:20).
~St Gregory of Sinai