I’ve been reading through Andrew Louth’s Introducing Eastern Orthodox Theology.  It’s a challenging book, I find, but I’m quite enjoying it.  In a section that discusses an Eastern Orthodox response to evolution, Fr. Andrew provides a translation of a few paragraphs from St. Gregory of Nyssa’s work, On the Creation of the Human and explains how St. Gregory and many of the Fathers of the Church understood the animal (and indeed plant-like) nature of humans and God’s calling for human beings to transform what is animal within themselves into virtue.  Keep in mind the word virtue comes from the Latin and means “manly.”  Or to put it into less sexist and more clear language: virtue manifests true humanity.  However, when human beings do not raise what is animal in themselves, then they of necessity pervert it into vice.  That is, a natural, even innocent, impulse will become either virtue or vice in a human being.  It is impossible for the impulse to remain merely animal and innocent.

Here is what Fr. Andrew says along with his translation of St. Gregory:

When the Fathers interpret Genesis, they see the human as sharing a great deal with animal, and indeed plant-like, creation.  The possession of reason, the gift of being in the image of God, makes the human distinctive, indeed raises the human to a position that transcends the animal and the plant-like, both as being nobler, and also as bearing responsibility for the ret of creation, but the human still shares a very great deal with the rest of creation, both animal and plant-like, and even with the inanimate creation.  St. Gregory of Nyssa, the younger brother of St. Basil the Great, discussed the nature of the human in his work, On the Creation of the Human, which he wrote to supplement his brother’s set of homilies on the Six Days of Creation, the Hexaemeron, as presented in Genesis.  Basil’s homilies are incomplete, for reasons unknown: the creation of man is only mentioned, not discussed.

In his work, Gregory deals at some length with the nature of the human.  His account draws on the accepted philosophical ideas of his day, not least Aristotle’s analysis of the human make-up.  At one point, Gregory tackles the idea that the human being has a soul that shares a great deal with the soul we find in animals, and indeed the soul we find in plants: the Greek word for soul, psyche, means ‘life’, and so the word soul suggest the principle of life that any living being has.  So the human man being is said to have an animal soul and a plant-like soul, as well as a rational or intellectual soul.  Yet a human being does not have three souls, rather the intellectual soul manifests itself at the animal and plant-like level, which the human shares with animals and plants. {Note: I think the word he is translating “intellect” may be referring to the Greek word nous because it is rather famously translated that way in the English version of the Philokalia—but I don’t know.  It’s a guess.}  What is meant to happen with humans is that the intellectual soul expresses itself through, and makes use of, the lower levels, the animal and plant-like.  But the Fall, as we have seen, has disturbed the harmony of God’s creation, and this is true at what one might call the psychological level {level of the soul}: instead of expressing itself through the animal and plant-like, the intellect finds itself serving the animal drives and plant-like needs (for nourishment, for example), and producing what we call beastial behaviour—which is really something distinctively human {i.e. not at all animal or plant-like}, though nothing to be proud of.  So the human has two aspects—one reaching towards the divine, the other succumbing to the animal—and is in fact poised on a watershed between affinity to the divine and affinity to lower creation.  Gregory puts it like this:

It seems to me that the human bears to contradictory likenesses—shaped in the divine aspect of his mind after the divine beauty, but also bearing, in the passionate impulses that arise in him, a likeness to the beastial nature.  Frequently his reason is reduced to beastiality, and obscures the better element by the worse through its inclination and disposition towards the animal.  For whenever anyone drags down the activity of thought to these, and forces reason to become the servant of the passions, there occurs a sort of distortion of the good character towards the irrational image, his whole nature being refashioned in accordance with this, as reason cultivates the new shoots of the passions, and little by little causes them to grow into a multitude; for once [reason] makes common cause with passion, it produces a thing and diverse crop of evils.

Thus our love of pleasure took its beginning from our likeness to the irrational creation, but was increased by human transgression, begetting such a variety of sinning flowing from pleasure, as is not to be found among the animals.  Thus the rising of anger is indeed akin to the impulse of the animals, but it is increased by the alliance with our process of thought.  For thence come resentment, envy, deceit, conspiracy, hypocrisy: all these are the result of the evil husbandry of the intellect.  For if the passion is stripped of this alliance with the process of thought, the anger that is left behind is short-lived and feeble—like a bubble, bursting as soon as it comes into being.  Thus the gluttony of pigs introduces covetousness, and the high spirit of the horse becomes the origin of pride; and everything that proceeds from the lack of reason in animal nature becomes vice by the wicked use of the intellect.  

So, therefore, on the contrary, if reason instead assumes sway over such emotions, each of them is transmuted into a form of virtue.  For anger produces courage, cowardice {produces} caution, fear {produces} obedience, hatred {produces} aversion from vice, the power of love {produces} the desire for what is truly beautiful. High spirit in our character raises our thought above the passions, and keeps it from bondage to what is base.  The great apostle, too, praises such a form of mental elevation when he bids us constantly to ‘set our minds on things that are above’ (Col. 3:2) and so we find that every such motion, when elevated by loftiness of mind, is conformed to the beauty after the divine image.

This is very much more subtle than—quite unfairly—attributing the worse characteristics of the human to animals; rather, the human shares a great deal with the animal world, but makes it human either by raising it to something that furthers our own assimilation to God, our process of deification, or by embroidering and developing it in characteristically human ways, fashioning vices that take their cue from innocent animal patterns of behaviour….

The world around us is telling us that our passions are natural, and in a sense the world is right.  Passions begin as natural animal impulses, but within the human mind, they cannot remain merely natural.  And here is where the world is wrong, tragically wrong.  The human soul is not merely an animal soul.  And thus the human mind, while it shares many things with the animals, is not merely an advanced animal mind.  The human mind is spiritually wired.  The human mind is exposed to the spiritual reality, both angelic and demonic, in ways animals are not.  Human beings were created on the frontier of physical and spiritual, sensual and noetic, creation. Human beings participate and function in both realities.  Consequently, when what arises from the animal, sensual, aspect of our nature enters our mind, it must be changed: either for better or worse.

And this is at least one way to understand where both the passions (or vices) and the virtues come from.