[5] Who was this prince; and why did the author stand in such need of his countenance as to dedicate to him this booklet in the humble and lengthy terms of apology which run through the greater part of the Introduction? It is Doctor S. Landauer’s opinion that, with this Essay, Ibn Sînâ began his career as a writer. After he had completed the sixteenth year of his age, he was summoned to the bedside of the suffering Sâmânid prince, Nûh ibn Mançûr, who resided at Bukhâra (See Ibn Khallikân’s Biographies), and succeeded in curing him. Then, followed a long period during which Ibn Sînâ removed from the Court of one Ruler to that of another, and was successively engaged in the service of various Petty Dynasties in Khurasân. If then this Essay was his maiden production--as Doctor Landauer assumes--the author was still quite young, and stood in need of the patronage he so earnestly implores. Furthermore there is a manuscript in Leyden, marked Codex 958, and numbered 1968 in the Catalogue, which is a small treatise on the soul by Ibn Sînâ, closing as follows: «I had produced a short essay on the exposition of the knowledge of the soul, and what is connected therewith, at the beginning of my career forty years ago, after the purely philosophical method of investigation. Whoso wishes to know that method, let him peruse it, for it is adapted to the seekers of research.» The «40 years ago» fit exactly, if students one assumes that the literary production referred to is the one he dedicated to «the Prince.» Now, the first prince he came in contact with was Nûh ibn Mançûr (ruled from 366-387 H. = 976-997 A.D., the Eighth of the Sâmânid Dynasty). Ibn Khallikân relates that Ibn Sînâ, at the age of 16 years, had begun to have a great reputation as a physician. Moreover the Latin translation in Florence of this essay bears in express words the dedication to Nûh. Result: Ibn Sînâ born in 370 H. = 980 A.D. Earliest Age as Treating Physician 386 H. = 996 Death of Nûh in Month of Ragab 387 H. = 997 Jule Death of Ibn Sînâ 428 H. = 1036 Between 386 and 428 lie the 40 years. SECTION FIRST =To Establish the Existence of the Spiritual Faculties, the Detailed Analysis of which I have undertaken.= Whoso wishes to describe anything whatsoever before proceeding to establish first its [6]reality of existence, such a one is counted by the wise among those who deviate from the broad beaten track of perspicuous statement. It is incumbent upon us, therefore, to first set to work to establish the existence of the spiritual powers, before starting to define each one of them singly, and enlarge upon it.