The difference between must and if you can.
1 Since the best thing for man is to become attached in his mind to God and divine things, and since it is impossible for man intensively to busy himself with a variety of things in order that man’s mind may be applied to God with greater liberty, counsels are given in the divine law whereby men are withdrawn from the busy concerns of the present life as far as is possible for one who is living an earthly life.
Now, this detachment is not so necessary to man for justice that its absence makes justice impossible; indeed, virtue and justice are not removed if man uses bodily and earthly things in accord with the order of reason. And so, divine law admonitions of this kind are called counsels, not precepts, inasmuch as man is urged to renounce lesser goods for the sake of better goods.
Notes This and the next argument put to rest various objections from those who take an overly literal read of scripture.
2 Moreover, in the general mode of human life, human concern is devoted to three items: first, to one’s own person, what he should do, or where he should spend his time; second, to the persons of those connected with him, chiefly his wife and children; and third, to the acquisition of external things, which a man needs for the maintenance of life.
So, to cut off solicitude for external things the counsel of poverty is given in the divine law, that is to say, so that one may cast off the things of this world with which his mind could be involved with some concern. Hence, the Lord says: “If You would be perfect, go sell what you have and give to the poor… and come, follow me” (Mat. 19:21). And to cut off concern for wife and children there is given man the counsel of virginity or continence. Hence, it is said in 1 Corinthians (7:25): “Now, concerning virgins, I have no commandment of the Lord, but I give counsel.” And giving the reason for this counsel, he adds: “He who is without a wife is solicitous for the things that belong to the Lord: how he may please God. But he who is with a wife is solicitous for the things of the world: how he may please his wife, and he is divided” (1 Cor. 7:32-33).
Finally, to cut off man’s solicitude even for himself there is given the counsel of obedience, through which man hands over the control of his own acts to a superior. Concerning which it is said: “Obey your prelates and be subject to them. For they watch as being ready to render an account of your souls” (Heb. 13:17).
Notes A counsel, not a law. Therefore you do not have to obey immoral orders. The excuse “I was just following orders” will not fly.
3 But, since the highest perfection of human life consists in the mind of man being detached from care, for the sake of God, and since the three counsels mentioned above seem most definitely to prepare one for this detachment, they appear to belong quite appropriately to the state of perfection; not as if they were perfections themselves, but that they are dispositions to perfection, which consists in being detached from care, for the sake of God. And the words of our Lord, when He advises poverty, definitely show this, for He says: “If you would be perfect, go sell what you have and give to the poor… and follow me” (Mat. 19:21), thus putting the perfection of life in the following of Him.
4 They may also be called the effects and signs of perfection. When the mind becomes attached to a thing with intense love and desire, the result is that it sets aside other things. So, from the fact that man’s mind is fervently inclined by love and desire to divine matters, in which it is obvious that perfection is located, it follows that he casts aside everything that might hold him back from this inclination to God: not only concern for things, for wife, and the love of offspring, but even for himself. And the words of Scripture suggest this, for it is said in the Canticle of Canticles (8:7): “if a man should give all the substance of his house for love, he will account it as nothing”; and in Matthew (13:45): “the kingdom of heaven is like to a merchant seeking good pearls, who, when he found one pearl of great price, went his way and sold all that he had and bought it”; and also in Philippians (3:7-8): “the things that were gain to me… I counted as dung, that I might gain Christ.”
5 So, since the aforesaid three counsels are dispositions to perfection, and are the effects and signs of perfection, it is fitting that those who pledge themselves to these three by a vow to God should be said to be in the state of perfection.
6 Now, the perfection to which these three counsels give a disposition consists in detachment of the mind for God. Hence, those who profess the aforesaid vows are called religious, in the sense that they offer themselves and their goods to God, as a special kind of sacrifice: as far as goods are concerned, by poverty; in regard to their body, by continence; and in regard to their will, by obedience. For religion consists in a divine cult, as was said above.