[27] Cato did not himself write on synonyms. But Isidore probably got this idea from the fact that synonyms were excerpted from his writings by later grammarians. See Teuffel, _History of Roman Literature_, 121, 6. [28] Migne, _P. L._ 83, col. 9. The _De Natura Rerum_[29] is a work of great importance for an understanding of Isidore’s view of the physical universe. The preface is of especial interest as giving some hints of his methods of literary work and of his attitude toward pagan writers. It is addressed to Sisebutus, who was king of the Visigoths from 612 to 620.[30] It runs as follows: [29] There is a critical edition of _De Natura Rerum_ by G. Becker, Berlin, 1857. [30] Isidore describes this ruler in his _History of the Goths_ as _scientia literarum magna ex parte imbutus_. See Migne, _P. L._ 83, col. 1073. Although, as I know, you excel in talent and eloquence and in the varied accomplishments of literature (_vario flore literarum_), you are still anxious for greater attainment, and you ask me to explain to you something of the nature and causes of things. I, on my part, have run over the works of earlier writers, and am not slow to satisfy your interest and desire, describing in part the system of the days and months; the goals of the year, as well, and the changes of the seasons; the nature also of the elements; the courses of the sun and moon, and the significance of certain stars;[31] the signs of the weather, too, and of the winds; and besides, the situation of the earth, and the alternate tides of the sea. And setting forth all things as they are written by the ancients, and especially in the works of catholic writers, we have described them briefly. For to know the nature of these things is not the wisdom of superstition, if only they are considered with sound and sober learning. Nay, if they were in every way far removed from the search for the truth, that wise king would by no means have said: “Ipse mihi dedit horum quae sunt scientiam veram ut sciam dispositionem coeli et virtutes elementorum, conversionum mutationes, et divisiones temporum, annorum cursus et stellarum dispositiones.” [31] “The higher meaning.” Compare _De Natura Rerum_, chapter 26, 4: “Per hunc Arcturum, id est, Septentrionem, Ecclesiam septenaria virtute fulgentem intelligimus.” Wherefore, beginning with the day, whose creation appears first in the order of visible things, let us expound those remaining matters as to which we know that certain men of the heathen and of the church have opinions, setting down in some cases both their thoughts and words, in order that the authority of the very words may carry belief.