Objection 1. It would seem that the notion of a state does not denote a condition of freedom or servitude. For "state" takes its name from "standing." Now a person is said to stand on account of his being upright; and Gregory says (Moral. vii, 17): "To fall by speaking harmful words is to forfeit entirely the state of righteousness." But a man acquires spiritual uprightness by submitting his will to God; wherefore a gloss on Psalm 32:1, "Praise becometh the upright," says: "The upright are those who direct their heart according to God's will." Therefore it would seem that obedience to the Divine commandments suffices alone for the notion of a state.
Objection 2. Further, the word "state" seems to denote immobility according to (1 Corinthians 15:48), "Be ye steadfast [stabiles] and immovable"; wherefore Gregory says (Hom. xxi in Ezech.): "The stone is foursquare, and is stable on all sides, if no disturbance will make it fall." Now it is virtue that enables us "to act with immobility," according to Ethic. ii, 4. Therefore it would seem that a state is acquired by every virtuous action.
Objection 3. Further, the word "state" seems to indicate height of a kind; because to stand is to be raised upwards. Now one man is made higher than another by various duties; and in like manner men are raised upwards in various ways by various grades and orders. Therefore the mere difference of grades, orders, or duties suffices for a difference of states.
On the contrary, It is thus laid down in the Decretals (II, qu. vi, can. Si Quando): "Whenever anyone intervene in a cause where life or state is at stake he must do so, not by a proxy, but in his own person"; and "state" here has reference to freedom or servitude. Therefore it would seem that nothing differentiates a man's state, except that which refers to freedom or servitude.
I answer that, "State," properly speaking, denotes a kind of position, whereby a thing is disposed with a certain immobility in a manner according with its nature. For it is natural to man that his head should be directed upwards, his feet set firmly on the ground, and his other intermediate members disposed in becoming order; and this is not the case if he lie down, sit, or recline, but only when he stands upright: nor again is he said to stand, if he move, but only when he is still. Hence it is again that even in human acts, a matter is said to have stability [statum] in reference to its own disposition in the point of a certain immobility or restfulness. Consequently matters which easily change and are extrinsic to them do not constitute a state among men, for instance that a man be rich or poor, of high or low rank, and so forth. Wherefore in the civil law [Dig. I, IX, De Senatoribus] (Lib. Cassius ff. De Senatoribus) it is said that if a man be removed from the senate, he is deprived of his dignity rather than of his state. But that alone seemingly pertains to a man's state, which regards an obligation binding his person, in so far, to wit, as a man is his own master or subject to another, not indeed from any slight or unstable cause, but from one that is firmly established; and this is something pertaining to the nature of freedom or servitude. Therefore state properly regards freedom or servitude whether in spiritual or in civil matters.
Reply to Objection 1. Uprightness as such does not pertain to the notion of state, except in so far as it is connatural to man with the addition of a certain restfulness. Hence other animals are said to stand without its being required that they should be upright; nor again are men said to stand, however upright their position be, unless they be still.
Reply to Objection 2. Immobility does not suffice for the notion of state; since even one who sits or lies down is still, and yet he is not said to stand.
Reply to Objection 3. Duty implies relation to act; while grades denote an order of superiority and inferiority. But state requires immobility in that which regards a condition of the person himself.
Source: Summa Theologica (New Advent)