Clement of Alexandria The Instructor Book II For the saying, "It is not a good tree which produces corrupt fruit, nor a corrupt tree which produces good fruit,"[116] Tertullian A Treatise on the Soul in order that they may be able to establish and settle their threefold theory, or "trinity," in all its characteristics as to the several natures, because "a good tree cannot produce evil fruit, nor a corrupt tree good fruit; and nobody gathers figs of thorns, nor grapes of brambles."[169] Tertullian Against Marcion Book I of his conceit from the simple passage of our Lord's saying, which has reference to human beings and not divine ones, wherein He disposes of those examples of a good tree and a corrupt one;[31]