But it is in chapter xlvii. of the _De Vita Propria_, which must have been written shortly before his death, that he lets the reader see most plainly how strong was the hold which this belief in a guardian spirit of his own had taken upon him. "It is an admitted truth," he writes, "that attendant spirits have protected certain men, to wit, Socrates, Plotinus, Synesius, Dion, Flavius Josephus, and myself. All of these have enjoyed prosperous lives except Socrates and me, and I, as I have said before, was at one time offered many and favourable opportunities for the achievement of happiness. But C. Caesar the dictator, Cicero, Antony, Brutus, and Cassius were also attended by mighty spirits, albeit malignant. For a long time I have been persuaded that I too had one, but by what method it gave me intelligence as to events about to happen, I could not exactly ascertain until I reached the seventy-fourth year of my age, the season when I began to write this record of my life. I now perceive that when I was in Milan in 1557, when my genius perceived what was hanging over me--how that my son on that same evening had promised to marry Brandonia Seroni, and that he would complete the nuptials the following day--it produced in me that palpitation of the heart of which I have already made mention, a weakness known to my genius alone, a manifestation which served to simulate a trembling of the bed." Cardan writes at length to show that the mysterious knocking which he and Rodolfo Sylvestro had heard during his imprisonment at Bologna, the peasant who entered his bed-chamber saying "_Te sin casa_," and divers other manifestations, going back as far as 1531--croaking of ravens, barking of dogs, and the ignition of fire-wood--must all have been brought about by the working of this powerful spirit. In 1570 there happened to him one of his everyday experiences of the presence of supernatural powers. In the middle of the night he was conscious of some presence walking about the room. It sat down beside him, and at the same time a loud noise arose from a chest which stood near. This phenomenon, he admits, might well have been the figment of a brain overburdened with thought; but suddenly his memory flies back to an experience of his twentieth year, upon which he proceeds to build a story, wild and fanciful even for his powers of imagination. "What man was it," he asks, "who sold me that copy of Apuleius when I was in my twentieth year, and forthwith went away? I indeed, at that time, had made only one essay in the literary arena, and had no knowledge of the Latin tongue; but in spite of this, and because the book had a gilded cover, I was imprudent enough to buy it. The very next day I found myself just as well versed in Latin as I am now. Moreover, almost at the same time I acquired knowledge of Greek and Spanish and French, sufficient for reading books written in these languages."