reject the Stoic doctrine that there are certain sensations so forcible as to produce an irresistible conviction of their truth. For these philosophers ascribe the full possession of this conviction to the sage alone, and he is not, nor can he be, one of the generality of mankind. Hence Cicero, who writes for these, gives his opinion that there are certain sensuous impressions in which from their permanence and force a man may safely trust, though he cannot assert them to be absolutely true. [71] This liberal and popular doctrine he is aware will be undermined by the absolute scepticism of the New Academy; [72] but he is willing to risk this, and to put his view forward as the best possible approximation to truth. With these ultimate principles Cicero, in his _De Natura Deorum_, approaches the questions of the existence of God and of the human soul. The bias of his own nobler nature led him to hold fast these two vital truths, but he is fully aware that in attempting to prove them the Stoics have used arguments which are not convincing. In the Tusculan disputations [73] he acknowledges the necessity of assuming one supreme Creator or Ruler of all things, endued with eternal motion in himself; and he connects this view with the affinity which he everywhere assumes to subsist between the human and divine spirit. With regard to the essence of the human soul he has no clear views; but he strenuously asserts its existence and phenomenal manifestation analogous to those of the Deity, and is disposed to ascribe to it immortality also. [74] Free Will he considers to be a truth of peculiar importance, probably from the practical consideration that on it responsibility and, therefore, morality itself ultimately rest.