On the Sacrifice of Abel and Cain (36-39)

For, as it is impossible to see without light, since neither colours nor eyes are sufficient for the comprehension of things which we arrive at by means of sight (for nature has made light beforehand to serve as a link to connect the two, by which the eye is brought near and adapted to colour, for the powers of both eye and of colour are equally useless in darkness), so in the same manner is the eye of the soul unable to comprehend anything whatever of the actions in accordance with virtue, unless it takes to itself labour as a coadjutor, as the eye borrows the assistance of light; for this, being placed in the middle, between the intellect and the good object which the intellect desires, and understanding the whole nature of both the one and the other, does itself

For, choose whatever good thing you please, and you will find that it owes its existence and all its strength and solidity to labour. Now, piety and holiness are good things, but still we are not able to attain to them without the worship of the gods, and the worship of them is combined with perseverance in labours. Again, prudence and courage and justice are all beautiful things and perfect goods, but still they are not to be acquired by laziness, and we must be content if they can be attained to by continued diligence. Now, since the organs of every soul are not able to support a familiarity with God and with virtue, as being a very intense and mighty harmony, they very often get lax and become remiss so as to descend from the highest unto those of more moderate character;

but, nevertheless, even in these moderate ones there is great labour requisite. Look at all those who practise the encyclical branches of what is called elementary instruction; look at those who cultivate the land, and at all who provide the means of subsistence by any regular business. These men are never free from care night or day, but always and continually, as it is said, they labour with hand and foot and with all their power, and never cease from suffering hardship, so as often to encounter even death from it.

But as those who are thus anxious to render their souls propitious must of necessity cultivate the virtues of the soul, so also they who purpose to render their bodies favourable to their objects, must cultivate health and those powers which are akin to health, and these too they cultivate with unremitting and ceaseless labours, being overwhelmed with care, arising from the faculties in them of which they are compounded.