"If man of himself could in a perfect manner know all things visible and invisible, it would indeed be foolish to believe what he does not see. But our manner of knowing is so weak that no philosopher could perfectly investigate the nature of even one little fly."

“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.”