Objection 1. It would seem that whoever is perfect is in the state of perfection. For, as stated above (3, ad 3), just as bodily perfection is reached by bodily growth, so spiritual perfection is acquired by spiritual growth. Now after bodily growth one is said to have reached the state of perfect age. Therefore seemingly also after spiritual growth, when one has already reached spiritual perfection, one is in the state of perfection.
Objection 2. Further, according to Phys. v, 2, movement "from one contrary to another" has the same aspect as "movement from less to more." Now when a man is changed from sin to grace, he is said to change his state, in so far as the state of sin differs from the state of grace. Therefore it would seem that in the same manner, when one progresses from a lesser to a greater grace, so as to reach the perfect degree, one is in the state of perfection.
Objection 3. Further, a man acquires a state by being freed from servitude. But one is freed from the servitude of sin by charity, because "charity covereth all sins" (Proverbs 10:12). Now one is said to be perfect on account of charity, as stated above (Article 1). Therefore, seemingly, whoever has perfection, for this very reason has the state of perfection.
On the contrary, Some are in the state of perfection, who are wholly lacking in charity and grace, for instance wicked bishops or religious. Therefore it would seem that on the other hand some have the perfection of life, who nevertheless have not the state of perfection.
I answer that, As stated above (Question 183, Article 1), state properly regards a condition of freedom or servitude. Now spiritual freedom or servitude may be considered in man in two ways: first, with respect to his internal actions; secondly, with respect to his external actions. And since according to (1 Samuel 16:7), "man seeth those things that appear, but the Lord beholdeth the heart," it follows that with regard to man's internal disposition we consider his spiritual state in relation to the Divine judgment, while with regard to his external actions we consider man's spiritual state in relation to the Church. It is in this latter sense that we are now speaking of states, namely in so far as the Church derives a certain beauty from the variety of states [Cf. 183, 2].
Now it must be observed, that so far as men are concerned, in order that any one attain to a state of freedom or servitude there is required first of all an obligation or a release. For the mere fact of serving someone does not make a man a slave, since even the free serve, according to (Galatians 5:13), "By charity of the spirit serve one another": nor again does the mere fact of ceasing to serve make a man free, as in the case of a runaway slave; but properly speaking a man is a slave if he be bound to serve, and a man is free if he be released from service. Secondly, it is required that the aforesaid obligation be imposed with a certain solemnity; even as a certain solemnity is observed in other matters which among men obtain a settlement in perpetuity.
Accordingly, properly speaking, one is said to be in the state of perfection, not through having the act of perfect love, but through binding himself in perpetuity and with a certain solemnity to those things that pertain to perfection. Moreover it happens that some persons bind themselves to that which they do not keep, and some fulfil that to which they have not bound themselves, as in the case of the two sons (Matthew 21:28-30), one of whom when his father said: "Work in my vineyard," answered: "I will not," and "afterwards... he went," while the other "answering said: I go... and he went not." Wherefore nothing hinders some from being perfect without being in the state of perfection, and some in the state of perfection without being perfect.
Reply to Objection 1. By bodily growth a man progresses in things pertaining to nature, wherefore he attains to the state of nature; especially since "what is according to nature is," in a way, "unchangeable" [Ethic. v, 7, inasmuch as nature is determinate to one thing. On like manner by inward spiritual growth a man reaches the state of perfection in relation to the Divine judgment. But as regards the distinctions of ecclesiastical states, a man does not reach the state of perfection except by growth in respect of external actions.
Reply to Objection 2. This argument also regards the interior state. Yet when a man passes from sin to grace, he passes from servitude to freedom; and this does not result from a mere progress in grace, except when a man binds himself to things pertaining to grace.
Reply to Objection 3. Again this argument considers the interior state. Nevertheless, although charity causes the change of condition from spiritual servitude to spiritual freedom, an increase of charity has not the same effect.
Source: Summa Theologica (New Advent)