But in the next generation there arrived in Rome a man whose teaching had so great an influence on the best type of educated Roman that, as we have already said, he may almost be regarded as a missionary.[551] We do not know for certain whether Panaetius wrote or taught about the nature or existence of the gods; but we do know that he discussed the question of divination[552] in a work [Greek: Peri pronoias], where he could hardly have avoided the subject. In any case the Stoic doctrines which he held, themselves ultimately derived from Plato and the Old Academy, were found capable in the hands of his great successor Posidonius of Rhodes of supplying a philosophical basis for the activity as well as the existence of the gods. These men, it must be repeated, were not merely professed philosophers, but men of the world, travellers, writing on a great variety of subjects; they were profoundly interested, like Polybius, in the Roman character and government; they became intimate with the finer Roman minds, from Scipio the younger to Cicero and Varro, and seem to have seen clearly that the old rigid Stoicism must be widened and humanised, and its ethical and theological aspects modified, if it were to gain a real hold on the practical Roman understanding. We have already seen[553] how their modified Stoic ethics acted for good on the best Romans of our period. In theology also they left a permanent mark on Roman thought; Posidonius wrote a work on the gods, which formed the basis of the speculative part of Varro's _Antiquitates divinae_, and almost certainly also of the second book of Cicero's de _Natura Deorum_[554]. Other philosophers of the period, even if not professed Stoics, may have discussed the same subjects in their lectures and writings, arriving at conclusions of the same kind.