It must further be noted that disbelief in a future life, as a philosophical principle, was not confined to the Epicureans. All philosophers except the Platonists and Pythagoreans were materialists; and no logical thinker who had once applied his mind to the subject could accept such an absurdity as the everlasting duration of a complex corporeal substance, whether consisting of gaseous or of fiery matter. A majority of the Stoics allowed the soul to continue its individual existence until, in common with the whole world, it should be reabsorbed into the elemental fire; but others looked forward to a more speedy extinction, without ceasing on that account to consider themselves orthodox members of the school. Of these the most remarkable instance is Marcus Aurelius. The great emperor was not blind to what seemed the enormous injustice of death, and did not quite see his way to reconciling it with the Stoic belief in a beneficent providence; but the difficulty of finding room for so many ghosts, and perhaps also the Heracleitean dogma of perpetual transformation, led him to renounce whatever hope he may at one time have cherished of entering on a new existence in some better world.[359] A similar consequence was involved in the principles of the Peripatetic philosophy; and Alexander of Aphrodisias, the famous Aristotelian commentator, who flourished about 200 A.D., affirms the perishable nature of the soul on his own account, and, with perfect justice, attributes the same belief to Aristotle himself.[360] Among the scientific and literary men who were not pledged to any particular school, we find the elder Pliny rejecting the belief in immortality, not only as irrational but as the reverse of consolatory. It robs us, he declares, of Nature’s most especial boon, which is death, and doubles the pangs of dissolution by the prospect of continued existence elsewhere.[361] Quintilian leaves the question undecided;[362] Tacitus expresses himself doubtfully;[363] and Galen, whose great physiological knowledge enabled him to see how fallacious were Plato’s arguments, while his philosophical training equally separated him from the materialists, also refuses to pronounce in favour of either side.[364] What Juvenal thought is uncertain; but, from his general tone, we may conjecture that he leant to the negative side.[365]