“Therefore I think that the moral virtues are not in us by nature wholly, for nothing can ever become used to that which is naturally contrary to it; as we see in the case of a stone, which although it were thrown upwards ten thousand times would never become used to move thither of itself; hence if virtue were as natural to us as weight is to the stone, we should never become used to vice. Nor, on the other hand, are the vices natural in this sense, for we should never be able to be virtuous; and it would be too unfair and foolish to chastise men for those defects that proceed from nature without our fault; and this errour would be committed by the law, which does not inflict punishment upon malefactors on account of their past errour (since what is done can not be undone), but has regard to the future, to the end that he who has erred may err no more nor be the cause of others erring through his bad example. And thus the law presumes that the virtues can be learned, which is very true; for we are born capable of receiving them and the vices also, and hence custom creates in us the habit of both the one and the other, so that we first practise virtue or vice, and then are virtuous or vicious. “The contrary is observed in things that are bestowed by nature, which we first have the power to practise and then do practise: as is the case with the senses; for first we are able to see, hear and touch, then we see, hear and touch, although also many of these functions are perfected by training. Wherefore good masters teach children not only letters, but also good and seemly manners in eating, drinking, speaking and walking, with certain appropriate gestures. 13.—“Therefore as in the other arts, so too in virtue it is necessary to have a master, who by instruction and good reminders shall arouse and awake in us those moral virtues whereof we have the seed enclosed and buried in our soul, and like a good husbandman shall cultivate them and open the way for them by freeing us from the thorns and tares of appetite, which often so overshadow and choke our minds as not to let them blossom or bring forth those happy fruits which alone we should desire to have spring up in the human heart.