Objection 1. It would seem that the perfection of the Christian life does not consist chiefly in charity. For the Apostle says (1 Corinthians 14:20): "In malice be children, but in sense be perfect." But charity regards not the senses but the affections. Therefore it would seem that the perfection of the Christian life does not chiefly consist in charity.
Objection 2. Further,'it is written (Ephesians 6:1)3): "Take unto you the armor of God, that you may be able to resist in the evil day, and to stand in all things perfect"; and the text continues (Ephesians 6:1)4,16), speaking of the armor of God: "Stand therefore having your loins girt about with truth, and having on the breast-plate of justice... in all things taking the shield of faith." Therefore the perfection of the Christian life consists not only in charity, but also in other virtues.
Objection 3. Further, virtues like other habits, are specified by their acts. Now it is written (James 1:4) that "patience hath a perfect work." Therefore seemingly the state of perfection consists more specially in patience.
On the contrary, It is written (Colossians 3:14): "Above all things have charity, which is the bond of perfection," because it binds, as it were, all the other virtues together in perfect unity.
I answer that, A thing is said to be perfect in so far as it attains its proper end, which is the ultimate perfection thereof. Now it is charity that unites us to God, Who is the last end of the human mind, since "he that abideth in charity abideth in God, and God in him" (1 John 4:16). Therefore the perfection of the Christian life consists radically in charity.
Reply to Objection 1. The perfection of the human senses would seem to consist chiefly in their concurring together in the unity of truth, according to (1 Corinthians 1:10), "That you be perfect in the same mind [sensu], and in the same judgment." Now this is effected by charity which operates consent in us men. Wherefore even the perfection of the senses consists radically in the perfection of charity.
Reply to Objection 2. A man may be said to be perfect in two ways. First, simply: and this perfection regards that which belongs to a thing's nature, for instance an animal may be said to be perfect when it lacks nothing in the disposition of its members and in such things as are necessary for an animal's life. Secondly, a thing is said to be perfect relatively: and this perfection regards something connected with the thing externally, such as whiteness or blackness or something of the kind. Now the Christian life consists chiefly in charity whereby the soul is united to God; wherefore it is written (1 John 3:14): "He that loveth not abideth in death." Hence the perfection of the Christian life consists simply in charity, but in the other virtues relatively. And since that which is simply, is paramount and greatest in comparison with other things, it follows that the perfection of charity is paramount in relation to the perfection that regards the other virtues.
Reply to Objection 3. Patience is stated to have a perfect work in relation to charity, in so far as it is an effect of the abundance of charity that a man bears hardships patiently, according to (Romans 8:3)5, "Who... shall separate us from the love of Christ? Shall tribulation? Or distress?" etc.
Source: Summa Theologica (New Advent)