From all that we have stated in this chapter, it is evident that it is man's duty to aim at performing acts that observe the proper mean, and not to desist from them by going to one extreme or the other, except for the restoration of the soul's health by having recourse to the opposite of that from which the soul is suffering. So, just as he who, acquainted with the science of medicine, upon noting the least sign of a change for the worse in his health, does not remain indifferent to it, but prevents the sickness from increasing to a degree that will require recourse to violent remedies, and just as when a man, feeling that one of his limbs has become affected, carefully nurses it, refraining from things that are injurious to it, and applying every remedy that will restore it to its healthy condition, or at least keep it from getting worse, likewise, the moral man will constantly examine his characteristics, weigh his deeds, and daily investigate his psychic condition; and if, at any time, he finds his soul deviating to one extreme or another, he will immediately hasten to apply the proper remedy, and not suffer an evil aptitude to acquire strength, as we have shown, by a constant repetition of that evil action which it occasioned. He is, likewise, bound to be mindful of his defects, and constantly to endeavor to remedy them, as we have said above, for it is impossible for any man to be free from all faults. Philosophers tell us that it is most difficult and rare to find a man who, by his nature, is endowed with every perfection, moral as well as mental. This thought is expressed often in the prophetical books, as, "Behold in his servants he putteth no trust, and his angels he chargeth with folly", "How can man be justified with God? or how can be pure one that is born of woman?", and Solomon says of mankind in general, "For no man is so righteous upon earth that he should do always good, and never sin".