20.  The soul is immortal, and all souls are alike both of men and women; for only the members of the body are distinguished Apelles, the heretic, attributed the difference of sex to the soul, which existing before the body impressed its sex upon it.  Tertull. On the Soul, c. xxxvi..  There is not a class of souls sinning by nature, and a class of souls practising righteousness by nature Irenæus I. vii. 5:  “They (the Valentinians) conceive of three kinds of men, spiritual, material, and animal.…These three natures are no longer found in one person, but constitute various kinds of men.…And again subdividing the animal souls themselves, they say that some are by nature good, and others by nature evil.”  Origen on Romans, Lib. VIII. § 10:  “I know not how those who come from the School of Valentinus and Basilides…suppose that there are souls of one nature which are always safe and never perish, and others which always perish, and are never saved.”:  but both act from choice, the substance of their souls being of one kind only, and alike in all.  I know, however, that I am talking much, and that the time is already long:  but what is more precious than salvation?  Art thou not willing to take trouble in getting provisions for the way against the heretics?  And wilt thou not learn the bye-paths of the road, lest from ignorance thou fall down a precipice?  If thy teachers think it no small gain for thee to learn these things, shouldest not thou the learner gladly receive the multitude of things told thee?