Letter 89 — On the Parts of Philosophy (§11)

“The Epicureans held that philosophy was twofold, natural and moral; they did away with the rational branch. Then, when they were compelled by the facts themselves to distinguish between equivocal ideas and to expose fallacies that lay hidden under the cloak of truth, they themselves also introduced a heading to which they give the name “forensic and regulative,” which is merely “rational” under another name, although they hold that this section is accessory to the department of “natural” philosophy.”