Article III: On the Quality of Human Law

St. Thomas, I-II, q. 95, a. 2 and 3.

270. Principle I. Human law is a derivation of natural law.

It is proved: law, since it is an ordination of reason, must be conformable to the rule of reason; for it is not true law unless it is just; the just is the same as what is right according to the rule of reason; therefore, insofar as law has something of justice or of rectitude of reason, so far does it have something of the power of law. But the first rule of reason is natural law. Therefore human law has the power of law insofar as it is derived from the law of nature. But if in anything it is discordant from it, it will no longer be law but a corruption of law (Gregory XVI, enc. Qui pluribus, November 9, 1846; Pius IX, enc. Quanta Cura, December 8, 1864).

271. Principle II. Human law is the complement of natural law.

It is proved: from natural law something can be derived 1) as a necessary conclusion from principles, for example, "one must not kill" from the fact that evil is to be done to no one; and this pertains not to human law alone but has the force of obligating also from the law of nature; 2) as a fitting conclusion or particular determination of a common and indeterminate principle, whether for directing men or for coercing them; and this has vigor immediately from human law alone. Thus, for example, that a contract is to be made in such a mode that justice is better provided for is a determination of the directive principle: contracts are to be entered according to justice; and that thieves are to be punished by prison rather than another penalty is a determination of the coercive principle: thieves are to be punished.

It is said: immediately, because all just human laws obligate mediately by force of this natural principle, that inferiors ought to obey superiors.

272. Principle III. Human law must be proportioned both to the end and to natural and divine law.

It is proved: for human law is a means to the end, and is a rule and measure ruled and measured by the superior natural law and eternal law of God; therefore it must be proportioned to these three. Hence:

1. insofar as it is proportioned to the law of God, it must be congruous to religion and consequently honorable, not contradicting eternal law;

2. insofar as it is conformable to the law of nature, it must be fitting to discipline, that is, a) as to object: just, or establishing that which is right according to reason; b) as to the faculty of agents or the power of subjects: possible and according to nature, because impossibilities are not to be imposed upon men, and according to the custom of the country, because man cannot live in society without bearing himself according to the manner of others; c) as to due circumstances: fitting to place and time;

3. insofar as it is proportioned to the end, it must be expedient for the safety or utility of men, and therefore a) necessary for removing evil or useful for attaining good; b) manifest, that is, clear so that it can be understood, lest it be a harm to men; c) conveniently handed down for the republic, that is, ordered to the common good.