I will be doing a series of posts commenting on the work On the Perfection of the Spiritual Life by Thomas Aquinas (parallel to the posts on evolution, faith, and theology).
Since certain persons, knowing nothing about perfection, have presumed to speak follies concerning the state of perfection, our purpose is to treat of perfection: what it is to be perfect; how perfection is acquired; what is the state of perfection; and what befits those who take up this state.
[Here Aquinas states the occasion that led him to write this work, his aim in writing it, and what he will consider in the main parts of the work. The occasion of this work was various attacks made on the religious orders, on the religious vows as means of attaining perfection, and on the occupations which religious could lawfully undertake. His aim is to treat of perfection [of the spiritual life] generally, and descend from there to consider how one attains perfection, what are the stable states of life oriented in a special manner to perfection, which are therefore called "states of perfection", and what works a religious community may take up.]
The Perfection of the Spiritual Life Simply Speaking is Found According to Charity
We must first consider that "perfect" is said in several ways. For something may be simply speaking perfect, or something may be called perfect in a certain respect. Something is simply speaking perfect when it attains to the end that belongs to it according to its proper nature, while something can be called perfect in a certain respect when it attains an end in regard to things accompanying its proper nature, as an animal is said to be perfect simply speaking, when it reaches the end that it lacks none of those things that constitute animal life: e.g., when it lacks nothing in number or disposition of its limbs, or the proper size of the body, or the power by which the activities of animal life are accomplished; an animal can be said to be perfect in a certain respect, however, if it is perfect in something that accompanies animal nature: e.g., if it is perfect in whiteness, or in odor, or something like this.
[Thomas's first aim is to establish what perfection is, what it means to be perfect. It is taken as a given, something understood as a matter of course, that the perfection which ultimately matters to a human and to a Christian, is spiritual perfection, being perfect in the spiritual life. But because the spiritual life, just like animal life, comprises many aspects–knowledge, decisions, attitudes, love, Thomas makes a general distinction about what it means to be perfect. A thing that has many aspects can be perfect in some particular aspect, but be lacking in other aspects, and perhaps more important ones. We cannot then say it is perfect, without qualifying our statement. Only when a thing is perfect in the respect that is most important or essential to it, can we say that it is perfect without needing to qualify ourselves (if we do qualify our statement, it will be to make explicit, perhaps, that there is some aspect of perfection that it is lacking; e.g., no matter how perfect a man's health is, it lacks the perfection of being incorruptible; he is able to die).]
Thus also a man is said to be simply speaking perfect in the spiritual life, with respect to that in which spiritual life primarily consists, while he can be called perfect in a certain respect, as regards anything that is connected with spiritual life. [Thomas notes that the general principle applies to the spiritual life; a man who is perfect in that which is essential to the spiritual life can be called perfect without adding a qualifier to "perfect".]
Now spiritual life consists primarily in charity, and he who does not have charity, is regarded as spiritually nothing. Hence the Apostle says, "If I have prophetic powers, and understand all mysteries and all knowledge, and if I have all faith, so as to remove mountains, but have not love, I am nothing" (1 Cor 13:2). Blessed John the Apostle also declares that the whole of spiritual life consists in love, saying, "We know that we have passed out of death into life, because we love the brethren. He who does not love abides in death" (1 John 3:14). [The next step: to be alive spiritually means to share in the life of God, the God who "is love", and this share in God's life is attained in the love of God, in charity. The quotes Thomas chooses here seem to pertain immediately to love of neighbor, though ultimately it is the same gift of charity by which we love God and neighbor.]
Therefore, it is he who is perfect in charity who is simply speaking perfect in the spiritual life. [The primary conclusion of the chapter. "To be perfect" without qualification means to be perfect in charity.] But some can be called perfect in a certain respect, as regards anything connected with the spiritual life. [The other side of the conclusion: one can be perfect in other aspects of spiritual life, and then one is said to be perfect in a certain respect.]
This can also be clearly shown from the words of Holy Scripture. [The conclusion just drawn was based on Scripture, but attained in a more abstract way; here Thomas illustrates the truth more directly by Scripture.] For the Apostle in Col 3:14 attributes perfection primarily to charity: for having enumerated many virtues, such as compassion, benignity, and humility, he adds, "But above all these things have charity, which is the bond of perfection" (Col 3:14). [Charity is the bond of perfection of all virtues, and so it is by charity that we are perfect in the most fundamental sense.] But some are also said to be perfect as regards understanding; for the same Apostle says, "Be babes in evil, but in sense be perfect." (1 Cor 14:20). Elsewhere in the same epistle, he says, "be perfect in the same mind and in the same judgment" (1 Cor. 1:10), although as was said, no matter how perfect knowledge a man has, without charity he is to be judged as nothing. So also a man may be said to be perfect in patience, which "has a perfect work," as St. James says, and in any other virtues. [Having cited examples of Scripture using perfection in a qualified sense, even though such perfection without love is not really worth anything, Thomas proceeds to the most extreme examples, of "perfection" used in regard to something bad.] This need not be surprising, for someone may be perfect in a bad thing, as when one speaks of "a perfect thief" or "a perfect robber." And Scripture also sometimes speaks this way: for it is said, "the fool's heart heart will work iniquity to perfect hypocrisy" (Isa 32:6).