Scripture consistently uses the term “darkness” to refer to that which is contrary to God's order and truth. Even in the very opening lines of Genesis the world is described as kind of primeval emptiness and without form or order: The earth was formless and void, and darkness was over the surface of the deep (Gen 1:2). But, Then God said, "Let there be light"; and there was light (Gen 1:3) and thus order began to be introduced. God spoke his word successively, and from this word there came order, from raw elements came that which was rational, orderly, and life-giving. 

It began with the first word, “Let there be light.” 

Down through Scripture, in passages too numerous to fully reproduce here, darkness consistently symbolized that which was contrary to God, to order and law. The theme echoed in the Ninth Plague of Exodus: there was pitch darkness in all the land of Egypt three days. They did not see one another, nor did anyone rise from his place for three days, but all the people of Israel had light where they lived (Ex 10:22-23). It echoes in the prophets. Through Ezekiel God spoke tenderly of his people saying I will care for My sheep and will deliver them from all the places to which they were scattered when it was cloudy and dark (Ez 34:12). 

And in St. John’s Gospel the battle between light and darkness is described. The prologue says The light shines in the darkness, and the darkness has not overcome it (Jn 1:5); yet still, in the third chapter of John, Jesus laments This is the verdict: Light has come into the world, but people loved darkness instead of light because their deeds were evil (Jn 3:19).  The darkness reaches its pinnacle when Judas goes out to betray the Lord. John says simply, it was night (Jn 13:30). 

St Paul picks up the theme in numerous places, warning that we walk no longer as the Gentiles walk, in the futility of their mind, being darkened in their understanding (Eph 4:17-19). And he sadly depicts the Greeks and Romans as those who suppress the truth and their senseless minds, darkened by sin, approved homosexual acts and many other forms of sin (Rom 1:17ff).

In our own times, almost an exact replica of the sick culture described in Romans 1, it is hard to describe our times is anything but dark.   

But whence this darkness, where did that come from? Surely there is a long philosophical trail one can trace. But I would propose here merely to focus on one particular aspect of the reason for darkness in our times.

In a word, the darkness is fueled by intemperance. For indeed, as Thomas teaches so well in the Summa, sins of intemperance have a particularly powerful role in darkening the intellect.

Temperance as a general virtue helps us to moderate excesses or defects regarding all aspects of life. However, St. Thomas in the Summa treats of it as a “special” virtue that is limited especially to the bodily appetites. This is because other virtues especially fortitude, exist to moderate spiritual matters.  (cf IIa, IIae, 141, art 1-3). 

And thus Thomas treats of temperance is a special virtue oriented especially toward moderating matters of taste and touch; and chief among the sins against intemperance are gluttony and lust, along with the related matters of drunkenness, immodesty, and incontinence. 

It is clear that we see that intemperance is severe and significant in our times. And this reflection underscores it as a chief cause, for the intellectual darkness of our time. While the carnal sins are not the most serious of the sins, (other things being equal, sins against the spirit are more serious), the carnal sins that emerge from intemperance are the most disgraceful. St. Thomas says why:

Intemperance is most disgraceful for two reasons. First, because it is most repugnant to human excellence, since it is about pleasures common to us and the lower animals, as stated above (141, 2,3). Wherefore it is written (Psalm 48:21): "Man, when he was in honor, did not understand: he hath been compared to senseless beasts, and made like to them." Secondly, [intemperance is most disgraceful] because it is most repugnant to man's clarity or beauty; inasmuch as the pleasures which are the matter of intemperance dim the light of reason from which all the clarity and beauty of virtue arises: wherefore these pleasures are described as being most slavish. (IIa, IIae, q 142, a 4)

So intemperance, while not the most egregious of sins, does have the powerful and disgraceful effect of darkening our minds. And this is especially so with sexual sins, so widespread and even “applauded” in our culture. 

But why do sexual sins darken the intellect more so than gluttony or other sins? Here too St. Thomas is insightful: 

In the sin of fornication the soul is the body’s slave in a special sense, because at the moment of sinning it can think of nothing else: whereas the pleasure of gluttony, although carnal, does not so utterly absorb the reason… (Ia IIae q 72.2 ad 4) 

Exactly. Sexual sin overwhelms the person in a way other sins do not. The mind gets preoccupied and then lost in the passion; and not just the passion of the moment, but often in a sort of passion that exists and grows in a gnawing sort of way. The mind becomes preoccupied and overwhelmed in an ongoing manner. Lust too easily becomes the consistent preoccupation of some. 

And in the fog of clouded and darkened intellects, some of the most foolish and nonsensical things are said and done related to sexual things. Some enter misguided marriages, others destroy good marriages for a fling, or a preference for pornography. Some risk and acquire diseases, others risk and destroy their relationships, their future, families, and children. There is divorce, cohabitation, unwed mothers, absent fathers, and a body-count of aborted children so numerous as to be almost unimaginable. 

And yet despite all this, due to darkened intellects, very few seem to be waking up, connecting the dots and realizing that horrible pain has come from the sexual intemperance of our times. Instead the darkness deepens, and many have doubled-down on the confusion. Social movements demanding acceptance for the most aberrant sexual practices have multiplied, to the point where many cannot even keep track of all the “options” that are now demanding approval.  The insanity of a twelve year old boy being able to say he thinks he is a girl and being taken seriously by his “parents” is outdistanced only by the collective insanity school board who takes him seriously and enacts a policy that boys can dress in the girls locker-room if they feel like a girl. 

Yes, intemperance, especially sexual intemperance, is the most disgraceful of sins because it has such an ability to darken our intellect. This insight of St. Thomas and other philosophers from saner times is writ large in our culture. 

A final observation of St. Thomas is both insightful and prophetic of our times: 

As the Philosopher himself says (Ethic iii. 12), the reason the reason why it is more shameful to be incontinent in lust than in anger, is that lust partakes less of reason; and in the same sense he says (Ethic. iii, 10) that sins of intemperance are most worthy of reproach, because they are about those pleasures which are common to us and irrational animals: hence, by these sins man is, so to speak, brutalized; for which same reason Gregory says (moral xxxiii, 11) that they are more shameful (Ia IIae 73, a 5, ad 3).

Yes, here is the crucial source of our darkness: intemperance, and most specifically the incontinence of lust. By it we are brutalized, become like unto irrational animals. And because some sins are contrary to nature, even lower than brute animals. 

Jesus warned, If then the light within you is darkness, how great is that darkness! (Mat 6:23) 

And it was night.