In investigating the truth the philosophers have broken through their own rules. Moses, however, showed himself more wise than they. The greater the dignity of wisdom, the more earnestly must we strive to gain it. Nature herself urges us all to do this.
122. It is said, therefore, that in investigating the truth, we must observe what is seemly. We ought to look for what is true with the greatest care. We must not put forward falsehood for truth, nor hide the truth in darkness, nor fill the mind with idle, involved, or doubtful matters. What so unseemly as to worship a wooden thing, which men themselves have made? What shows such darkness as to discuss subjects connected with geometry and astronomy (which they approve of), to measure the depths of space, to shut up heaven and earth within the limits of fixed numbers, to leave aside the grounds of salvation and to seek for error?
123. Moses, learned as he was in all the wisdom of the Egyptians, did not approve of those things, but thought that kind of wisdom both harmful and foolish. Turning away therefrom, he sought God with all the desire of his heart, and thus saw, questioned, heard Him when He spoke. Who is more wise than he whom God taught, and who brought to nought all the wisdom of the Egyptians, and all the powers of their craft by the might of his works? He did not treat things unknown as well known, and so rashly accept them. Yet these philosophers, though they do not consider it contrary to nature, nor shameful for themselves to worship, and to ask help from an idol which knows nothing, teach us that these two things mentioned in the words just spoken, which are in accordance both with nature and with virtue, ought to be avoided.
124. The loftier the virtue of wisdom is, the more I say we ought to strive for it, so that we may be able to attain to it. And that we may have no ideas which are contrary to nature, or are disgraceful, or unfitting, we ought to give two things, that is, time and care, to considering matters for the sake of investigating them. For there is nothing in which man excels all other living creatures more than in the fact that he has reason, seeks out the origin of things, thinks that the Author of his being should be searched out. For in His hand is our life and death; He rules this world by His nod. And to Him we know that we must give a reason for our actions. For there is nothing which is more of a help to a good life than to believe that He will be our judge, Whom hidden things do not escape, and unseemly things offend, and good deeds delight.
125. In all men, then, there lies, in accordance with human nature, a desire to search out the truth, which leads us on to have a longing for knowledge and learning, and infuses into us a wish to seek after it. To excel in this seems a noble thing to mankind; but there are only few who attain to it. And they, by deep thought, by careful deliberation, spend no little labour so as to be able to attain to that blessed and virtuous life, and to approach its likeness in their actions. “For not he that says to Me Lord, Lord, shall enter into the kingdom of heaven, but he that does those things that I say.” To have a desire for knowledge without actions to correspond— well! I do not know whether that carries anything more with it.
Source: On the Duties of the Clergy (New Advent)