On several occasions I have been asked to express verbally or in writing some thoughts about the so-called preventive system, which is in general use in our houses. Through lack of time I have so far been unable to meet these wishes; but as I now intend to print the rules of the houses, which until now have nearly always been used traditionally, I think it opportune to give a brief sketch, which may perhaps serve as an outline to a small book which I am preparing and hope to finish, if God gives me life enough, my sole purpose being to help in the difficult art of the education of the young. Wherefore I shall explain: in what the preventive system consists; why it ought to be preferred; and its practical application and its advantages.