Locke and “ad”

In IV, xvii, 19-22 of his Essay, Locke employs Latin labels for four kinds of argument, of which one (ad hominem) was already in circulation and one (ad judicium) has never had much currency. The present proposal seeks to locate and clarify what Locke was aiming to describe, and to contrast what he says with some subsequent uses that have been made of these labels as if they named fallacies. Though three of the four kinds of argument that Locke picks out are often less than decisive, he casts no aspersion on the legitimacy of their use in debate.