And as those almonds are called empty in which the contents are worthless, not those in which there is nothing; so also we call those heretics empty, who are destitute of the counsels of God and the traditions of Christ; bitter, in truth, like the wild almond, their dogmas originating with themselves, with the exception of such truths as they could not, by reason of their evidence, discard and conceal.
Clement of Alexandria
The Stromata, Book VII
Chapter XVI