From Dom Guéranger's The Liturgical Year.
The fundamental rule of Christian life is, as almost every page of the Gospel tells us, that we should live out of the world, separate ourselves from the world, hate the world. The world is that ungodly land which Abraham, our sublime model, is commanded by God to quit. It is that Babylon of our exile and captivity, where we are beset with dangers. The beloved disciple cries out to us: 'Love not the world, nor the things which are in the world. If any man love the world, the charity of the Father is not in him.’ Our most merciful Jesus, at the very time when He was about to offer Himself as a sacrifice for all men, spoke these awful words: 'I pray not for the world.' When we were baptized, and were signed with the glorious and indelible character of Christians, the condition required of us, and accepted, was that we should renounce the works and pomps of the world (which we expressed under the name of Satan); and this solemn baptismal promise we have often renewed.
But what is the meaning of our promise to renounce the world? Is it that we cannot be Christians, unless we flee into the desert and separate ourselves from our fellow-creatures? Such cannot be God’s will for all, since, in that same Scripture, wherein He commands us to flee from the world, He also tells us what are our duties to each other, and sanctions and blesses those ties which He Himself has willed should exist among us. His apostle, also, tells us to use this world as though we did not use it. It is not, therefore, forbidden us to live in, and to use, the world. Then, what means this renouncing of the world? Can there be contradiction in God’s commandments? Is it possible that we are condemned to wander blindly on the brink of a precipice, into which we must at last inevitably fall?
There is neither contradiction nor snare. If by the world, we mean these visible things around us which God created in His power and goodness; if we mean this outward world, which He made for His own glory and our benefit; it is worthy of its divine Author, and to us, if we but use it aright, is a ladder whereby our souls may ascend to their God. Let us gratefully use this world; go through it, without making it the object of our hope; not waste upon it that love, which God alone deserves; and ever be mindful, that we are not made for this, but for another and a happier, world.
But the majority of men are not thus prudent in their use of the world. Their hearts are fixed upon it, and not upon heaven. Hence it was, that when the Creator deigned to come into this world, in order that He might save it, the world knew Him not. Men were called after the name of the object of their love. They shut their eyes to the light; they became darkness; God calls them 'the world.’
In this sense, then, the world is everything that is opposed to our Lord Jesus Christ, that refuses to recognize Him, and that resists His divine guidance. Those false maxims which tend to weaken the love of God in our souls; which recommend the vanities that fasten our hearts to this present life; which cry down everything that can raise us above our weaknesses or vices; which decoy and gratify our corrupt nature by dangerous pleasures, which, far from helping us to the attainment of our last end, only mislead us—all these are ‘the world.’
This world is everywhere, and holds a secret league within our very hearts. Sin has brought it into this exterior world created by God for Himself, and has given it prominence. Now, we must conquer it, and trample upon it, or we shall perish with it. There is no being neutral; we must be its enemies, or its slaves. During these three days, its triumphs are fearful; and thousands of those who, at their Baptism, swore eternal enmity to it, are enrolling themselves its votaries. Let us pray for them; but let us also tremble for ourselves; and that our courage may not fail us, let us ponder those consoling words, which our Saviour, at His last Supper, addressed to His eternal Father. He is speaking of His disciples, and He says: 'Father! I have given them Thy word, and the world hath hated them, because they are not of the world, as I also am not of the world. I pray not, that Thou shouldst take them out of the world, but that Thou shouldst keep them from evil.'
As an appropriate conclusion of this day, we may use this formula of the Ambrosian liturgy. It puts two truths in contrast: the spiritual indifference of worldlings, and the dread severity of God’s future judgment.
(Dominica in Quinquagesima)
Jucunda est præsens vita, et transit: terribile est, Christe, judicium tuum, et permanet. Quapropter incertum amorem relinquamus, et de infinito timore cogitemus, clamantes: Christe, miserere nobis.
Sweet is this present life, but it passes away; terrible, O Christ, is thy judgment, and it endures for ever. Let us, therefore, cease to love what is unstable, and fix our thoughts on the fear of what is eternal; saying; Christ, have mercy upon us!
 St. John ii. 15.
 Ibid., xvii. 9.
 1 Cor. vii. 31.
 St. John i. 10.
 St. John xvii. 14, 15.