Diogenes Laertius Vitae philosophorum 7.1.105

[105] Hence of these latter some are taken by preference, others are rejected, whereas indifference in the other sense affords no ground for either choosing or avoiding.

Of things indifferent, as they express it, some are preferred, others rejected. Such as have value, they say, are preferred, while such as have negative, instead of positive, value are rejected. Value they define as, first, any contribution to harmonious living, such as attaches to every good; secondly, some faculty or use which indirectly ¹ contributes to the life according to nature: which is as much as to say any assistance brought by wealth or health towards living a natural life; thirdly, value is the full equivalent of an appraiser, as fixed by an expert acquainted with the facts—as when it is said that wheat exchanges for so much barley with a mule thrown in. ²