But just how prolonged it is difficult to say. For already as early as 1665 almost four-fifths of the _Ethics_ seems to have been written. We learn as much from a letter Spinoza wrote to one of his friends promising to send him the "third part" of his philosophy up to the eightieth proposition. From the letter it is fairly clear that at that time the _Ethics_ was divided into three, not five, parts. Also, in letters written that same year to William Blyenbergh one finds expressed some of the chief conclusions published five years later in the _Tractatus Theologico-Politicus_. And Spinoza wrote, at this early period, not conjecturally or speculatively, but as one writes who knows the firm and tested grounds of his belief. Why the _Ethics_, in final form, began to circulate privately only two or three years before Spinoza's death, and why his work on _The Improvement of the Understanding_ and his _Political Treatise_ were left unfinished, must remain something of an insoluble philosophico-literary mystery. The only book Spinoza published in his own lifetime above his own name was his _Principles of Descartes' Philosophy Geometrically Demonstrated_ with an appendix of _Cogitata Metaphysica_ which he had dictated to a youth (one "Cæsarius") "to whom (he) did not wish to teach (his) own opinions openly." Discretion, as he had already learned and later formally stated and proved, was not inconsonant with rational valor. The only other book Spinoza published in his lifetime--the _Tractatus Theologico-Politicus_--bore on its title page Spinoza's initials only, and the name of a fictitious Hamburg publisher. When Spinoza heard, some time later, that a Dutch translation of this work was being prepared, he earnestly beseeched his friends to forestall its publication (which they did) because only its Latin dress saved it from being officially proscribed. It was then an open secret who the author was. Spinoza's personal rule to incur as little official displeasure as possible made him abandon his final literary project entertained in 1675. When he began negotiations for the publication of the _Ethics_ a rumor spread that he had in press a book proving that God does not exist. Complaint was lodged with the prince and magistrates. "The stupid Cartesians," Spinoza wrote Oldenburg "being suspected of favoring me, endeavored to remove the aspersion by abusing every where my opinions and writings, a course which they still pursue." In the circumstances, Spinoza thought it wisest to delay publication till matters would change. But, apparently, they did not change, or change sufficiently. The _Ethics_ was first published about a year after Spinoza's death.