He calls their attention to an important point, in what is now styled Pedagogics, or the Science of Education. It is, that, in the form now sent out, the Fathers had taken pains to explain their reasons for arriving at conclusions. That would not be done in the System to be drawn up later, which would contain only the statement of directions for all to follow. In these words, we have a most important distinction laid down between the science which underlies the system of education, and the practical method itself which rests upon the science. The _Ratio Studiorum_, as subsequently promulgated, is a practical method. The science is sketched, as need arises, in the preliminary _Ratio_ of 1586. At the same time, Father Aquaviva despatched another letter, about which he says, in a postscript to the foregoing, that the six points provisionally laid down in it are to be subjected to the same examination as the preliminary _Ratio_ itself. In this supplementary epistle, he premises that it will require much time and consideration to issue the final code of rules; and therefore, as a direction for the time being, he issues the following:-- First, Professors shall adhere to St. Thomas Aquinas as their standard in theology. Secondly, they shall take care, in their manner of teaching, always to consolidate faith and piety. Thirdly, he lays down a principle of still wider application, and one which seems vital in the whole theory and practice of teaching: "Let no one defend any opinion which is judged by the generality of learned men to go against the received tenets of philosophers and theologians, or the common consent of theological schools." This touches a vital element in education. If we suppose that the teacher's art lies, not in giving forth the lucubrations of his own private thoughts and theories, but in imparting solid results, approved and ascertained, to those who come for such results, and wish to receive them in the most approved way, then the Professor in his chair ought not to mistake himself for the author in his study, nor should he practise on living men, whose life is all before them, what he might, with more propriety, first practise on the leisured world, and test elsewhere, either in the printed page, or in conference with his equals. The Professor, as such, is not the original investigator. In mathematics, he is notoriously not so. In that branch, the best teacher is the man who walks along a definite line, turns neither to the right nor left, and finishes in a definite time; or else his scholars will never finish. To a certain degree, the same holds in all courses. If a man is theorizing, when he ought to be instructing, he goes off the line of perfect system, however much pains he takes with his matter; just as much as if, taking no pains whatever, he neglected his matter altogether, went behind it, or around it, gave histories of his branch, methods of teaching it, and