During the years that this Opus has been in hand, (and in head and heart also) nothing was expunged as if it had become obsolete because the persons therein alluded to had departed like shadows, or the subjects there touched on had grown out of date; but much was introduced from time to time where it fitted best. Allusions occur in relation to facts which are many years younger than the body of the chapter in which they have been grafted, thus rendering it impossible for any critic, however acute, to determine the date of any one chapter by its contents. What Watts has said of his own Treatise upon the Improvement of the Mind may therefore with strict fidelity be applied to this book, which I trust, O gentle Reader, thou wilt regard as specially conducive to the improvement of thine. “The work was composed at different times, and by slow degrees. Now and then indeed it spread itself into branches and leaves, like a plant in April, and advanced seven or eight pages in a week; and sometimes it lay by without growth, like a vegetable in the winter, and did not increase half so much in the revolution of a year. As thoughts occurred to me in reading or meditation, or in my notices of the various appearances of things among mankind, they were thrown under appropriate heads, and were, by degrees, reduced to such a method as the subject would admit. The language and dress of these sentiments is such as the present temper of mind dictated, whether it were grave or pleasant, severe or smiling. And a book which has been twenty years in writing may be indulged in some variety of style and manner, though I hope there will not be found any great difference of sentiment.” With little transposition Watts' words have been made to suit my purpose; and when he afterwards speaks of “so many lines altered, so many things interlined, and so many paragraphs and pages here and there inserted,” the circumstances which he mentions as having deceived him in computing the extent of his work, set forth the embarrassment which the commentators will find in settling the chronology of mine.