The birth of this little work is due entirely to chance, and more to a kind of entertainment than to a serious plan. While conversing with a young nobleman who, at a tender age, displayed a very sound and discerning mind, a gentleman told him that when he was young he had found a man who helped him master part of logic in two weeks. This speech prompted another person who was present, and who had no great esteem for this science, to reply in jest that if the young nobleman wanted to take the trouble, he would take it upon himself to teach him everything useful about logic in four or five days. After discussing this extravagant proposal for a while, they resolved to make the attempt. But since ordinary logic books were thought to be neither short nor precise enough, they decided to create an abridged version just for the young nobleman.

This was our sole aim when we began the work, and we thought it would not take us more than a day. But once the work was under way, so many new thoughts came to mind that we had to write them down to unburden ourselves. So instead of one day it took us four or five to write the body of this Logic, to which we have since made various additions.