And the following appear to me to be childish assertions, viz., that “no good general and leader of great multitudes was ever betrayed; nor even a wicked captain of robbers and commander of very wicked men, who seemed to be of any use to his associates; but Jesus, having been betrayed by his subordinates, neither governed like a good general, nor, after deceiving his disciples, produced in the minds of the victims of his deceit that feeling of good-will which, so to speak, would be manifested towards a brigand chief.”
Now one might find many accounts of generals who were betrayed by their own soldiers, and of robber chiefs who were captured through the instrumentality of those who did not keep their bargains with them. But grant that no general or robber chief was ever betrayed, what does that contribute to the establishment of the fact as a charge against Jesus, that one of His disciples became His betrayer? And since Celsus makes an ostentatious exhibition of philosophy, I would ask of him, If, then, it was a charge against Plato, that Aristotle, after being his pupil for twenty years, went away and assailed his doctrine of the immortality of the soul, and styled the ideas of Plato the merest trifling? And if I were still in doubt, I would continue thus: Was Plato no longer mighty in dialectics, nor able to defend his views, after Aristotle had taken his departure; and, on that account, are the opinions of Plato false?
Or may it not be, that while Plato is true, as the pupils of his philosophy would maintain, Aristotle was guilty of wickedness and ingratitude towards his teacher? Nay, Chrysippus also, in many places of his writings, appears to assail Cleanthes, introducing novel opinions opposed to his views, although the latter had been his teacher when he was a young man, and began the study of philosophy. Aristotle, indeed, is said to have been Plato's pupil for twenty years, and no inconsiderable period was spent by Chrysippus in the school of Cleanthes; while Judas did not remain so much as three years with Jesus. But from the narratives of the lives of philosophers we might take many instances similar to those on which Celsus founds a charge against Jesus on account of Judas.
Even the Pythagoreans erected cenotaphs to those who, after betaking themselves to philosophy, fell back again into their ignorant mode of life; and yet neither was Pythagoras nor his followers, on that account, weak in argument and demonstration.
Source: Against Celsus (New Advent)