Cicero believed in the existence of one supreme Creator and Governor of the universe, and also in His spiritual nature;[852] but his belief is rather the result of instinctive conviction, than of the proofs derived from philosophy; for as to them, he is, as on other points, uncertain and wavering. He disbelieved the popular mythical religion; but, uncertain as to what was the truth, he would not have that disturbed which he looked upon as a political engine.[853] Amidst the doubtful and conflicting reasons, respecting the human soul and man’s eternal destiny, there is no doubt that, although he finds no satisfactory proof, he is a believer in immortality.[854] It is unnecessary to pursue the subject of his philosophical creed any further, because it is not a system, but only a collection of precepts, not of investigations. Its materials are borrowed, its illustrations alone novel. But, nevertheless, the study of Cicero’s philosophical works is invaluable, in order to understand the minds of those who came after him. It must not be forgotten, that not only all Roman philosophy after his time, but a great part of that of the middle ages, was Greek philosophy filtered through Latin, and mainly founded on that of Cicero. Cicero’s works on speculative philosophy generally consist of—(1.) _The Academics_, or a history and defence of the belief of the New Academy. (2.) The _De Finibus Bonorum et Malorum_, dialogues on the supreme good, the end of all moral action. (3.) _The Tusculanæ Disputationes_, containing five independent treatises on the fear of death, the endurance of pain, the power of wisdom over sorrow, the morbid passions, the relation of virtue to happiness. In these treatises Stoicism predominates, although opinions are adduced from the whole range of Greek philosophy. (4.) _Paradoxa_, in which the six celebrated Stoical paradoxies are touched upon in a light and amusing manner. (5.) A dialogue in praise of philosophy, named after Hortensius. (6.) Translations of the Timæus and Protagoras of Plato. Of these last three treatises only a few fragments remain. His moral philosophy comprehends—(1.) The _De Officiis_, a Stoical treatise on moral obligations, addressed to his son Marcus, at that time a student at Athens. (2.) The unequalled little essays on Friendship and Old Age. A few words also are preserved of two books on Glory, addressed to Atticus; and one which he wrote on the Alleviation of Grief when bereaved of his beloved daughter.[855] He left one theological work in three parts: the first part is on the “Nature of the Gods;” the second on the “Science of Divination;” the third on “Fate,” of which an inconsiderable fragment is extant. His office of augur probably suggested to him the composition of these treatises.