Being is intrinsically good. We all know this. This is what we see in a purring cat: it is most content when it can simply be itself, within itself. This is also why, analogically, we say a well tuned engine "purrs": it is being able to be itself, to be an engine without constraint. And while happiness is not a warm gun, a warm gun is happy in its own way, for it is radiating the fullness of its being as a firing weapon. Why else do so many people find guns so alluring? Such a small clump of matter can generate such a dramatic change in the face of being. It is the same goodness of being that we see in a sleeping baby: it does nothing, can do nothing, but is superior to us precisely in its immersion in sheer being. All this and more is good just because it is.
What does this mean? It means that being--existence--is not morally neutral. The world is and therefore the world is good: finality is coterminous with existence. We will to live because the goodness of being animates the deepest levels of our appetitive being. As St. Thomas says, a donkey cannot desire to be a tiger, since this would mean the destruction of what it is in itself. (Cf. the outrage of the cat and the donkey in Shrek 3 when they are transmogrified into each other's body.) All things, just in virtue of being, desire to continue in being: and this is a form of desire at all levels of being. We sense, in turn, that anything which is more completely "being" than ourselves, is somehow also morally better--more desirable--than ourselves.
Alas, under the guise of sickness, death, fear, loss, disillusionment, and so on, our own shallowness and progressive diminution of being is all too apparent. As such, we leap from one being to another in a vain attempt to tap into the source of Being Itself. Only by relinquishing all specific beings, however, can we hope to swim in the sea of Being Itself (just as a man can only hope to survive at sea by casting his trinkets into the water so he can stay afloat). As St. Jerome puts it, "Christum nudum nudus sequitur" (Follow a naked Christ naked). Once we "intuit" Being as such, we have only two choices: either a retreat to fragmentary idols of being or an act of total adoration and thanks to Being Itself for giving us a share of itself. If "the intuition of Being" (Maritain, Gilson, et al.) does not issue in gratitude, it is not a genuine intuition of Being as the source and medium of all good. Further, if the emergence of gratitude in the face of Being cannot terminate in giving thanks to a Giver, it is the hollowest gratitude, and not worthy of the name, at which point non-being becomes more desirable than being. As Chesterton (nodding to Dante Gabriel Rosetti) said, "The worst moment for the atheist is when he is really thankful and has nobody to thank. ... All goods look better when they look like gifts." As such, a love of being in the act of being itself without a love for the Being Who is the Act of Being itself, is the greatest metaphysical and ethical travesty man can bring upon himself.
All beings are, then, ontotropic: all things seek to maintain their own thingness and to increase it, if, that is, they possess an immanent principle of growth and motion. Just as plants lean towards the light and stretch their roots towards moisture, so finite beings naturally lean towards greater being and stretch their inner capacities towards that which activates them. None of this need be "conscious", but in the case of humans, it is quite often a conscious, intellectual drive. This is why, unlike non-intellectual animals, humans can desire to become tigers, or dolphins, or etc. It is by abstracting the intentional form of what-a-dolphin-is that we can "transplant" ourselves, in an intentional mode, into that form of being, while still preserving the subsistent vitality of our own Self as intellectual beings. Because the intellect becomes what it conceives, we in fact become dolphins and tigers by the mutual bond of intentional being in ourselves and in those creatures. All that prevents us from actually crossing that bridge to dolphinhood is, first, our lack of adequate metaphysical power to actualize such a potency by overcoming, second, the material limitations of our formal nature. We can conceive of "being made of cheese" but we can't bring it about since cheese is simply not an adequate material for existentiating the human form; neither is the human form an adequate metaphysical principle for raising cheese to sufficiently complex levels of formal order that it can existentiate the human form.
In any case, to return to the human ontotropism: its parallels with plants' phototropism is less than merely coincidental, for the Source of Being Himself is also the Light of Lights. It is only by shining in His Light that we are actual beings. Otherwise, we are overshadowed as mere potential essences in their super-actual light of His own sovereign Donation of Being. Indeed, possibility is only coherent if some principle of choice is integral to Being itself, a coherence sheer naturalism cannot provide, since all that is, on naturalism, necessarily is, and the possible becomes totally vacuous in contrast to the eternally-necessarily actual. Nature being devoid of any will and wisdom, benevolent or otherwise, cannot not be of its own actual character, which includes all sub-entities within it.
All things are intelligible in the Light of God as it shines on that which He makes a substantial medium for receiving the light in the first place. The more a being is open to that light, the more it will (ontotropically) swell in that light. By contrast, beings who decrease in their initial quantum and mode of being, will lose more and more ontological "surface area", whereby they will only diminish even more. It is precisely this cycle which clarifies much of the riddle of evil. For the divine wrath is not a positive infliction imposed on sinful beings, but is rather a negative superposition of light upon what should be a medium for its reflection. Evil is nothing--a lacuna in being--and so we can imagine "the evil within us" as holes and tears in the fabric of our being. As these holes grow, they let more of the Light pass through, and we become that much darker. The punishment we feel--the absence of the warmth of Divine Light--is but the negative superposition of Light which is meant for us, but which can find no surface to illuminate. Evil is nothing and its punishment is its own vacuity. Evil is literally invisible to God, since it is literally that-which-is-not, that which cannot be seen in the Divine Light. Insofar as it cannot be seen ("Adam, where are you hiding?"), it cannot be healed.