To teach rules for the interpretation of Scripture is not a superfluous task
1. There are certain rules for the interpretation of Scripture which I think might with great advantage be taught to earnest students of the word, that they may profit not only from reading the works of others who have laid open the secrets of the sacred writings, but also from themselves opening such secrets to others. These rules I propose to teach to those who are able and willing to learn, if God our Lord do not withhold from me, while I write, the thoughts He is wont to vouchsafe to me in my meditations on this subject. But before I enter upon this undertaking, I think it well to meet the objections of those who are likely to take exception to the work, or who would do so, did I not conciliate them beforehand. And if, after all, men should still be found to make objections, yet at least they will not prevail with others (over whom they might have influence, did they not find them forearmed against their assaults), to turn them back from a useful study to the dull sloth of ignorance.
Source: Christian Doctrine (New Advent)