Equality of man:
Declaration of Independence: All men are created equal; they are endowed by their Creator with certain inalienable rights.
Robert Bellarmine: All men are equal, not in wisdom or grace, but in the essence and nature of mankind (De Laicis, c.7) There is no reason why among equals one should rule rather than another (ibid.). Let rulers remember that they preside over men who are of the same nature as they themselves. (De Officus Princ. c. 22). Political right is immediately from God and necessarily inherent in the nature of man (De Laicis, c. 6, note 1).
St. Thomas Aquinas: Nature made all men equal in liberty, though not in their natural perfections (II Sent., d. xliv, q. 1, a. 3. ad 1).
The function of government:
Declaration of Independence: To secure these rights governments are instituted among men.
Bellarmine: It is impossible for men to live together without someone to care for the common good. Men must be governed by someone lest they be willing to perish (De Laicis, c. 6).
St. Thomas: To ordain anything for the common good belongs either to the whole people, or to someone who is the viceregent of the whole people (Summa, la llae, q. 90, a. 3).
The source of power:
Declaration of Independence: Governments are instituted among men, deriving their just powers from the consent of the governed.
Bellarmine: It depends upon the consent of the multitude to constitute over itself a king, consul, or other magistrate. This power is, indeed, from God, but vested in a particular ruler by the counsel and election of men (De Laicis, c. 6, notes 4 and 5). The people themselves immediately and directly hold the political power (De Clericis, c. 7).
St. Thomas: Therefore the making of a law belongs either to the whole people or to a public personage who has care of the whole people (Summa, la llae, q. 90, a. 3). The ruler has power and eminence from the subjects, and, in the event of his despising them, he sometimes loses both his power and position (De Erudit. Princ. Bk. I, c. 6).
The right to change the government:
Declaration of Independence: Whenever any form of government becomes destructive of these ends, it is the right of the people to alter or abolish it, and to institute a new government…Prudence, indeed, will dictate that governments long established should not be changed for light and transient reasons.
Bellarmine: For legitimate reasons the people can change the government to an aristocracy or a democracy or vice versa (De Laicis, c. 6). The people never transfers its powers to a king so completely but that it reserves to itself the right of receiving back this power (Recognitio de Laicis, c. 6).
St. Thomas: If any society of people have a right of choosing a king, then the king so established can be deposed by them without injustice, or his power can be curbed, when by tyranny he abuses his regal power (De Rege et Regno, Bk. I, c. 6).