Objection 1. It would seem that none should enter religion but those who are practiced in the observance of the commandments. For our Lord gave the counsel of perfection to the young man who said that he had kept the commandments "from his youth." Now all religious orders originate from Christ. Therefore it would seem that none should be allowed to enter religion but those who are practiced in the observance of the commandments.
Objection 2. Further, Gregory says (Hom. xv in Ezech., and Moral. xxii): "No one comes suddenly to the summit; but he must make a beginning of a good life in the smallest matters, so as to accomplish great things." Now the great things are the counsels which pertain to the perfection of life, while the lesser things are the commandments which belong to common righteousness. Therefore it would seem that one ought not to enter religion for the purpose of keeping the counsels, unless one be already practiced in the observance of the precepts.
Objection 3. Further, the religious state, like the holy orders, has a place of eminence in the Church. Now, as Gregory writes to the bishop Siagrius [Regist. ix, Ep. 106], "order should be observed in ascending to orders. For he seeks a fall who aspires to mount to the summit by overpassing the steps." [The rest of the quotation is from Regist. v, Ep. 53, ad Virgil. Episc.]. "For we are well aware that walls when built receive not the weight of the beams until the new fabric is rid of its moisture, lest if they should be burdened with weight before they are seasoned they bring down the whole building" (Dist. xlviii, can. Sicut neophytus). Therefore it would seem that one should not enter religion unless one be practiced in the observance of the precepts.
Objection 4. Further, a gloss on Psalm 130:2, "As a child that is weaned is towards his mother," says: "First we are conceived in the womb of Mother Church, by being taught the rudiments of faith. Then we are nourished as it were in her womb, by progressing in those same elements. Afterwards we are brought forth to the light by being regenerated in baptism. Then the Church bears us as it were in her hands and feeds us with milk, when after baptism we are instructed in good works and are nourished with the milk of simple doctrine while we progress; until having grown out of infancy we leave our mother's milk for a father's control, that is to say, we pass from simple doctrine, by which we are taught the Word made flesh, to the Word that was in the beginning with God." Afterwards it goes on to say: "For those who are just baptized on Holy Saturday are borne in the hands of the Church as it were and fed with milk until Pentecost, during which time nothing arduous is prescribed, no fasts, no rising at midnight. Afterwards they are confirmed by the Paraclete Spirit, and being weaned so to speak, begin to fast and keep other difficult observances. Many, like the heretics and schismatics, have perverted this order by being weaned before the time. Hence they have come to naught." Now this order is apparently perverted by those who enter religion, or induce others to enter religion, before they are practiced in the easier observance of the commandments. Therefore they would seem to be heretics or schismatics.
Objection 5. Further, one should proceed from that which precedes to that which follows after. Now the commandments precede the counsels, because they are more universal, for "the implication of the one by the other is not convertible" [Categor. ix], since whoever keeps the counsels keeps the commandments, but the converse does not hold. Seeing then that the right order requires one to pass from that which comes first to that which comes after, it follows that one ought not to pass to the observance of the counsels in religion, without being first of all practiced in the observance of the commandments.
On the contrary, Matthew the publican who was not practiced in the observance of the commandments was called by our Lord to the observance of the counsels. For it is stated (Luke 5:28) that "leaving all things he... followed Him." Therefore it is not necessary for a person to be practiced in the observance of the commandments before passing to the perfection of the counsels.
I answer that, As shown above (Question 188, Article 1), the religious state is a spiritual schooling for the attainment of the perfection of charity. This is accomplished through the removal of the obstacles to perfect charity by religious observances; and these obstacles are those things which attach man's affections to earthly things. Now the attachment of man's affections to earthly things is not only an obstacle to the perfection of charity, but sometimes leads to the loss of charity, when through turning inordinately to temporal goods man turns away from the immutable good by sinning mortally. Hence it is evident that the observances of the religious state, while removing the obstacles to perfect charity, remove also the occasions of sin: for instance, it is clear that fasting, watching, obedience, and the like withdraw man from sins of gluttony and lust and all other manner of sins.
Consequently it is right that not only those who are practiced in the observance of the commandments should enter religion in order to attain to yet greater perfection, but also those who are not practiced, in order the more easily to avoid sin and attain to perfection.
Reply to Objection 1. Jerome (Super Matth. xix, 20) says: "The young man lies when he says: 'All these have I kept from my youth.' For if he had fulfilled this commandment, 'Thou shalt love thy neighbor as thyself,' why did he go away sad when he heard: Go, sell all thou hast and give to the poor?" But this means that he lied as to the perfect observance of this commandment. Hence Origen says (Tract. viii super Matth.) that "it is written in the Gospel according to the Hebrews that when our Lord had said to him: 'Go, sell all thou hast,' the rich man began to scratch his head; and that our Lord said to him: How sayest thou: I have fulfilled the law and the prophets, seeing that it is written in the law: Thou shalt love thy neighbor as thyself? Behold many of thy brethren, children of Abraham, are clothed in filth, and die of hunger, whilst thy house is full of all manner of good things, and nothing whatever hath passed thence to them. And thus our Lord reproves him saying: If thou wilt be perfect, go, etc. For it is impossible to fulfil the commandment which says, Thou shalt love thy neighbor as thyself, and to be rich, especially to have such great wealth." This also refers to the perfect fulfilment of this precept. on the other hand, it is true that he kept the commandments imperfectly and in a general way. For perfection consists chiefly in the observance of the precepts of charity, as stated above (Question 184, Article 3). Wherefore in order to show that the perfection of the counsels is useful both to the innocent and to sinners, our Lord called not only the innocent youth but also the sinner Matthew. Yet Matthew obeyed His call, and the youth obeyed not, because sinners are converted to the religious life more easily than those who presume on their innocency. It is to the former that our Lord says (Matthew 21:31): "The publicans and the harlots shall go into the kingdom of God before you."
Reply to Objection 2. The highest and the lowest place can be taken in three ways. First, in reference to the same state and the same man; and thus it is evident that no one comes to the summit suddenly, since every man that lives aright, progresses during the whole course of his life, so as to arrive at the summit. Secondly, in comparison with various states; and thus he who desires to reach to a higher state need not begin from a lower state: for instance, if a man wish to be a cleric he need not first of all be practiced in the life of a layman. Thirdly, in comparison with different persons; and in this way it is clear that one man begins straightway not only from a higher state, but even from a higher degree of holiness, than the highest degree to which another man attains throughout his whole life. Hence Gregory says (Dial. ii, 1): "All are agreed that the boy Benedict began at a high degree of grace and perfection in his daily life."
Reply to Objection 3. As stated above (Question 184, Article 6) the holy orders prerequire holiness, whereas the religious state is a school for the attainment of holiness. Hence the burden of orders should be laid on the walls when these are already seasoned with holiness, whereas the burden of religion seasons the walls, i.e. men, by drawing out the damp of vice.
Reply to Objection 4. It is manifest from the words of this gloss that it is chiefly a question of the order of doctrine, in so far as one has to pass from easy matter to that which is more difficult. Hence it is clear from what follows that the statement that certain "heretics" and "schismatics have perverted this order" refers to the order of doctrine. For it continues thus: "But he says that he has kept these things, namely the aforesaid order, binding himself by an oath [Referring to the last words of the verse, and taking 'retributio,' which Douay renders 'reward,' as meaning 'punishment']. Thus I was humble not only in other things but also in knowledge, for 'I was humbly minded'; because I was first of all fed with milk, which is the Word made flesh, so that I grew up to partake of the bread of angels, namely the Word that is in the beginning with God." The example which is given in proof, of the newly baptized not being commanded to fast until Pentecost, shows that no difficult things are to be laid on them as an obligation before the Holy Ghost inspires them inwardly to take upon themselves difficult things of their own choice. Hence after Pentecost and the receiving of the Holy Ghost the Church observes a fast. Now the Holy Ghost, according to Ambrose (Super Luc. 1:15), "is not confined to any particular age; He ceases not when men die, He is not excluded from the maternal womb." Gregory also in a homily for Pentecost (xxx in Ev.) says: "He fills the boy harpist and makes him a psalmist: He fills the boy abstainer and makes him a wise judge [Daniel 1:8-17]," and afterwards he adds: "No time is needed to learn whatsoever He will, for He teaches the mind by the merest touch." Again it is written (Ecclesiastes 8:8), "It is not in man's power to stop the Spirit," and the Apostle admonishes us (1 Thessalonians 5:19): "Extinguish not the Spirit," and (Acts 7:51) it is said against certain persons: "You always resist the Holy Ghost."
Reply to Objection 5. There are certain chief precepts which are the ends, so to say, of the commandments and counsels. These are the precepts of charity, and the counsels are directed to them, not that these precepts cannot be observed without keeping the counsels, but that the keeping of the counsels conduces to the better observance of the precepts. The other precepts are secondary and are directed to the precepts of charity; in such a way that unless one observe them it is altogether impossible to keep the precepts of charity. Accordingly in the intention the perfect observance of the precepts of charity precedes the counsels, and yet sometimes it follows them in point of time. For such is the order of the end in relation to things directed to the end. But the observance in a general way of the precepts of charity together with the other precepts, is compared to the counsels as the common to the proper, because one can observe the precepts without observing the counsels, but not vice versa. Hence the common observance of the precepts precedes the counsels in the order of nature; but it does not follow that it precedes them in point of time, for a thing is not in the genus before being in one of the species. But the observance of the precepts apart from the counsels is directed to the observance of the precepts together with the counsels; as an imperfect to a perfect species, even as the irrational to the rational animal. Now the perfect is naturally prior to the imperfect, since "nature," as Boethius says (De Consol. iii, 10), "begins with perfect things." And yet it is not necessary for the precepts first of all to be observed without the counsels, and afterwards with the counsels, just as it is not necessary for one to be an ass before being a man, or married before being a virgin. On like manner it is not necessary for a person first of all to keep the commandments in the world before entering religion; especially as the worldly life does not dispose one to religious perfection, but is more an obstacle thereto.
Source: Summa Theologica (New Advent)