I have included in thirty-six books twenty thousand topics, all worthy of attention, gained by the careful perusal of one hundred select authors, and of about two thousand volumes, of which a few only are in the hands of the studious, on account of the obscurity of the subjects. To these I have made considerable additions of things, which were either not known to my predecessors, or which have been lately discovered. Nor can I doubt but that there still remain many things which I have omitted; for I am a mere mortal, and one that has many occupations. I have, therefore, been obliged to compose this work at interrupted intervals, by night as well as by day, so that you will find that I have not been idle even during this period. The day I devote to you, exactly portioning out my sleep to the necessity of my health, and contenting myself with this reward, that while we are musing on these subjects, as Varro says, we are adding to the length of our lives; for life properly consists in being awake. I consider it to be courteous and to indicate an ingenuous modesty, to acknowledge the sources whence we have derived assistance, and not to act as most of those have done whom I have examined. For I must inform you, that in comparing various authors with each other, I have discovered, that some of the latest and most dignified writers have transcribed, word for word, from former works, without making any acknowledgment; not avowedly rivalling them, in the manner of Virgil, or with the candor of Cicero, who, in his treatise “De Republica,” professes to coincide in opinion with Plato, and in his Essay on Consolation for his Daughter, says that he follows Crantor, and, in his Offices, Panæcius; volumes, which, as you well know, ought not merely to be always in our hands, but to be learned by heart. For it is surely the mark of a perverted mind and a bad disposition, to prefer being caught in a theft to returning what we have borrowed, especially when we have acquired capital, by usurious interest.