I said indeed to your fathers, that they ought early to lead you to marriage: but nevertheless neither are you without liability to punishment. For if there were not other young men also, more numerous than you, living in chastity, both formerly, and now, there would perhaps be some excuse for you. But if there are, how can you say, that we were not able to restrain the flame of lust? For they, who have been able, are your accusers, in that they are partakers of the same nature. Hear Paul saying, “Follow after peace...and the sanctification, without which no man shall see the Lord.” Is not this threat sufficient to terrify you? Do you see others continuing altogether in chastity, and in gravity passing their lives; and cannot you command yourself even so long as the period of youth? Do you see others ten thousand times overcoming pleasure, and cannot you once refrain? With your leave, I will tell you the cause. For youth is not the cause, since then all young men would be dissolute. But we thrust ourselves into the fire. For when you go up to the theater, and sit feasting your eyes with the naked limbs of women, for the time indeed you are delighted, but afterwards, you have nourished thence a mighty fever. When you see women exhibited as it were in the form of their bodies and spectacles and songs containing nothing else but irregular loves: such a woman, it is said, loved such a man, and not obtaining him, hanged herself; and unlawful loves having mothers for their object; when you receive these things by hearing also, and through women, and through figures, yea, and even through old men, (for many there put masks upon their faces, and play the parts of women,) tell me, how will you be able to continue chaste afterwards, these narratives, these spectacles, these songs occupying your soul, and dreams of this sort henceforth succeeding. For it is the nature of the soul for the most part to raise visions of such things, as it wishes for and desires in the daytime. Therefore when you there both see base actions, and hear baser words, and receive indeed the wounds but do not apply the remedies, how will not the sore naturally be increased? How will not the disease become more intense; and in a much greater degree than in our bodies? For if we were willing, our will admits of correction more easily than our bodies. For there indeed drugs, and physicians, and time are required, but here it is sufficient having but the will, to become both good and bad. So that you have rather admitted the disorder. When therefore we gather to us indeed the things that injure, but pay no regard to the things that benefit, how can there ever be any health?
On this account Paul said, “even as the Gentiles who knew not God.” Let us be ashamed, let us be afraid, if the Gentiles, that know not God, are often chaste. Let us turn for shame, when we are worse than they. It is easy to achieve chastity, if we will, if we withdraw ourselves from those things that are injurious, since it is not even easy to avoid fornication, if we will not. For what is more easy than to walk in the market-place? But from the excess of laziness it has become difficult, not only in the case of women, but sometimes even in that of men. What is more easy than to sleep? But we have made even this difficult. Many however of the rich toss themselves through a whole night, from their not waiting for the need of sleep, and then sleeping. And in short nothing is difficult, when men are willing; as nothing is easy, when they are unwilling; for we are masters of all these things. On this account the Scripture says, “If you be willing and hear me.” And again, “If you be unwilling, and hear not.” So that all depends upon being willing or unwilling. On this account we both are punished and are praised. But may it be ours, being of those who are praised, to obtain the promised blessings, by the grace and lovingkindness, etc.
Source: Homilies on First Thessalonians (New Advent)