In his essay The Natural, the Connatural, and the Unnatural he writes:
According to what might be called the lower meaning, the natural is the spontaneous, the haphazard, the unimproved: Think of Adam and Eve in the jungle, or for that matter, think of the jungle itself. From this point of view, a human being is at his most natural when he is driven by raw desires, "doing what comes naturally," as we say. But according to what might be called the higher meaning, the natural is what perfects us, what unfolds the inbuilt purposes of our design, what unlocks our directed potentialities. Think this time of Adam and Eve in the Garden, not the jungle, or for that matter, think of the Garden itself. From this point of view, a human being is most genuinely "doing what comes naturally" when he at his best and bravest and truest -- when he fulfills his creational design, when he "comes into his own." The lower way of speaking makes nature and second nature enemies. The higher makes them friends, at least potentially.
While talk of design and purpose must, I think, at least reference the challenges of philosophical Darwinism or empiricism, Budsiszewski's exploration gives the reader much to appreciate. His distinction between nature in potentia and "second nature," nature as actualized, must be kept clear in all discussions of human nature.
Take his description of habit and custom:
St. Thomas says that something can be connatural to a being insofar as it becomes natural through habituation, because "custom is a second nature." What he has in mind here is the way that habits and customs -- and, at another level, divine graces -- fill in the blanks, so to speak, which the generalities of nature leave undetermined. The result is that we acquire new inclinations to certain things, and come to find pleasure in things in which we did not find pleasure before. There are all sorts of varieties of second-nature connaturality, for example the connaturality of the lover with the beloved, whereby our nature adapts itself to the thing which, or to the person whom, we love.
The generalities of human nature, those discovered through philosophical or scientific inquiry, cannot forget the place of custom. It is in the domain of custom, too, that character and personality are most at play, whether in fiction or in reality.
Heresiologists make poor dramatists and social critics because they believe mistakes or differences about human or divine nature drive human behavior, when in fact it is the particular flaws and perfections of individual or collective habit that have the most motive power. These heresy-hunters call hubris Pelagianism, despair Calvinism, and impiety Gnosticism. Would that intellectual error were the only cause of sin! Education and argument would then suffice to correct the wicked.
Budsiszewski shows that mankind is capable of far more crookedness:
Not only can a man come to love what is contrary to his connatural good -- he can come to hate what conduces to his connatural good. In other words, he can learn to loath those things which tend to the very happiness that he is fashioned, by nature, to seek. Evil of a particular kind will become second nature to him even though it continues to be contrary to first nature -- but just because it has become second nature to him, he will have difficulty recognizing it as evil.
How does one cure a wicked habit when it is not recognized as wicked, when evil is one's good? Rational correction has its place, but perhaps external coercion and internal self-revulsion are the only other remedies short of divine intervention. Examples of external coercion are too familiar, ranging from social pressure to legal punishment.
Self-revulsion, however, needs more examination. Perhaps every sin contains within itself its own destruction. The sated glutton realizes his doom after the last gulp leaves him empty, or the wrathful pundit flinches upon seeing his recorded rage. Budsiszewski cites one woman who rejected her self-destruction after seeing others in extremis just down her vicious path. Call it the car-wreck effect.
This self-recognition constitutes a virtue of its own, and of course sin is best fought with true virtue.
Budsiszewski further references the Angelic Doctor in discussing how sin is a misdirected good. But the saint supplies us with an implicit rebuke of Romantic sentimentalism:
Evil is never loved except under the aspect of good, that is to say, in so far as it is good in some respect, and is considered as being good simply. And thus a certain love is evil, in so far as it tends to that which is not simply a true good. It is in this way that man "loves iniquity," inasmuch as, by means of iniquity, some good is gained; pleasure, for instance, or money, or such like.
(S.T. I-II, Q. 27, ad 1.)
No one can, without hinting at tragedy, say "Love conquers all" after reading this description of an "evil love."