"Reason may be employed in two ways to establish a point: firstly, for the purpose of furnishing sufficient proof of some principle, as in natural science, where sufficient proof can be brought to show that the movement of the heavens is always of uniform velocity. Reason is employed in another way, not as furnishing a sufficient proof of a principle, but as confirming an already established principle, by showing the congruity of its results, as in astrology the theory of eccentrics and epicycles is considered as established, because thereby the sensible appearances of the heavenly movements can be explained; not, however, as if this proof were sufficient, forasmuch as some other theory might explain them."

“Nothing is in the intellect that was not first in the senses.”

“With regard to the abuse of authority, this also may come about in two ways. First, when what is ordered by an authority is opposed to the object for which that authority was constituted (if, for example, some sinful action is commanded or one which is contrary to virtue, when it is precisely for the protection and fostering of virtue that authority is instituted). In such a case, not only is there no obligation to obey the authority, but one is obliged to disobey it, as did the holy martyrs who suffered death rather than obey the impious commands of tyrants. Secondly, when those who bear such authority command things which exceed the competence of such authority; as, for example, when a master demands payment from a servant which the latter is not bound to make, and other similar cases. In this instance the subject is free to obey or disobey.”

“The order of authority derives from God, as the Apostle says [in Romans 13:1-7]. For this reason, the duty of obedience is, for the Christian, a consequence of this derivation of authority from God, and ceases when that ceases. But, as we have already said, authority may fail to derive from God for two reasons: either because of the way in which authority has been obtained, or in consequence of the use which is made of it. There are two ways in which the first may occur. Either because of a defect in the person, if he is unworthy; or because of some defect in the way itself by which power was acquired, if, for example, through violence, or simony or some other illegal method.”

“Jesus Christ: Bene scripsísti de me, Thoma; quam ergo mercédem accípies? Aquinas: Non áliam, Dómine, nisi teípsum.”

“Raynalde, non possum, quia omnia quae scripsi videntur mihi palae. Replying to Reginald of Piperno: Videntur mihi palae respectu eorum quae vidi et revelata sunt mihi.”

“Omne verum a quocumque dicatur a Spiritu Sancto est.”