 Introductory material to the final (1683) edition includes a Preface (added 1683), a Foreword and First Discourse (1662), and a Second Discourse (added 1664). The First Discourse lays out the plan of the Logic, explaining that its main purpose is to educate judgment to make it more precise. This is seen as instrumental for making the speculative sciences more useful. Thus the Logic contains not only a treatment of correct reasoning, but also examples of how reasoning can go wrong. The Second Discourse offers a reply to objections made to the first edition. The main point is to justify the critical treatment of Aristotle on the ground that knowing how a great mind can err can help others avoid making the same mistakes. But it also takes pains to point out that the Logic owes some things to Aristotle’s Analytics and other works. The main text that then follows is about the four mental operations with one Part devoted to each.