De Plantatione

So that while we are outside of the promised land, we should not be able to cultivate such trees; and this is very natural;

for as long as the mind has not entered upon the path of wisdom, but turns aside and wanders out of the road, it cares only for the trees which do not admit of being cultivated or used for food of men—trees which are barren and useless, and which, though they bear, bear no fruit which is eatable.