In this fable he explains the common but erroneous supposition that knowledge and the conformity of the will, knowing and acting, are convertible terms. Of this error, he, in his essay of Custom and Education, admonishes his readers, by saying: “Men’s thoughts are much according to their inclination; their discourse and speeches according to their learning and infused opinions, but their deeds are after as they have been accustomed; Æsop’s Damsel, transformed from a cat to a woman, sat very demurely at the board-end till a mouse ran before her.” In the fable of the Sirens he exhibits the same truth, saying: “The habitation of the Sirens was in certain pleasant islands, from whence, as soon as out of their watchtower they discovered any ships approaching, with their sweet tunes they would first entice and stay them, and, having them in their power, would destroy them; and, so great were the mischiefs they did, that these isles of the Sirens, even as far off as man can ken them, appeared all over white with the bones of unburied carcasses; by which it is signified that albeit the examples of afflictions be manifest and eminent, yet they do not sufficiently deter us from the wicked enticements of pleasure.” The following is the account of the different editions of this work: The first was published in 1609. In February 27, 1610, Lord Bacon wrote to Mr. Mathew, upon sending his book _De Sapientia Veterum_:— “MR. MATHEW: I do very heartily thank you for your letter of the 24th of August, from Salamanca; and in recompense therefore I send you a little work of mine that hath begun to pass the world. They tell me my Latin is turned into silver, and become current: had you been here, you should have been my inquisitor before it came forth; but, I think, the greatest inquisitor in Spain will allow it. But one thing you must pardon me if I make no haste to believe, that the world should be grown to such an ecstasy as to reject truth in philosophy, because the author dissenteth in religion; no more than they do by Aristotle or Averroes. My great work goeth forward; and after my manner, I alter even when I add; so that nothing is finished till all be finished. This I have written in the midst of a term and parliament; thinking no time so possessed, but that I should talk of these matters with so good and dear a friend. And so with my wonted wishes I leave you to God’s goodness. “From Gray’s Inn, Feb. 27, 1610.” And in his letter to Father Fulgentio, giving some account of his writings, he says: “My Essays will not only be enlarged in number, but still more in substance. Along with them goes the little piece _De Sapientia Veterum_.” In the Advancement of Learning he says:—