Aquaviva's first letter to the Society was concerned chiefly with the qualities which superiors should possess--especially those of vigilance, sweetness and strength. His second was more universal, and dealt with the necessity of a constant renewal of the spiritual life. To him the Society is indebted for the "Directorium," or guide of the Spiritual Exercises. Under his administration the "Ratio Studiorum," or scheme of studies, was produced. It was the result of fifteen years of collaboration (1584-99) by a number of the most competent scholars that could be found in the Society. It covers the whole educational field from theology down to the grammar of the lower classes, exclusive, however, of the elements. Of course, this "Ratio" has not escaped criticism, for scarcely anything the Society ever attempted has had that good fortune. Thus, to take one out of many, Michelet bemoans the fact that "the Ratio has been; in operation for 300 years and has not yet produced a man." Such a charge, of course, does not call for discussion. The greatest service that Aquaviva rendered the Society, and for which it will ever bless his memory is that he saved it from destruction in a fight that ran through the thirty years of his Generalate, and in which he found opposed to him Popes, kings, and princes, along with the terrible authority of the Spanish Inquisition and, worst of all, a number of discontented members of the Order, banded together and resorting to the most reprehensible tactics to alter completely the character of the Institute and to rob it of that Catholicity which constitutes its glory and its power.