Treatise the Fortieth, comprehending twenty-four discourses on the subject of speech and writing, and the senses external and internal; with, under God's assistance, the preliminary chapter of the Zád-ul-Musafarín, composed by Hakím Nasar Khosru, surnamed Hujat, the Guide.
This work, which comprises seven-and-twenty parts or dissertations (in the original), I have been contented to bring under four discourses, or lectures, as a sufficient conclusion to the key of my dissertation on the repository of meanings. It is a composition of not less than eight hundred years standing, by that genuine philosopher and guide to the true principles of science whose name is above recorded, and whom we acknowledge to have been a lineal and no remote descendant of our venerated Prophet, and who continues to the present day to be the master and instructor of the wisest of the moderns in the sphere of the understanding. To his descent we have the testimony of his own words in the following couplet:—“I, who am the Prophet's truest heir—I, Nasar, the son of Khosru, son of Háreth.” Now Háreth was one among the children of Khorasan's royal Imám: accordingly, all such as have treated on the knowledge of things appertaining to the faculties of the human understanding, have diligently directed their studies to this excellent work, and thus acquired for themselves, distinguished renown.