AD JUDICIUM Argument
From the Latin judicium, meaning “legal action; judgment; capacity to judge.”
1. Ad judicium, the only “instructive” argument
In his Essay Concerning Human Understanding (1690), John Locke contrasts the ad judicium argument, which he considers valid, with other types of argument, that he holds to be fallacious: the arguments ad ignorantiam, ad hominem and ad verecundiam (Lat. verecundia, modesty); see collections 2.
The argument ad judicium is defined as:
The using of proofs drawn from any of the foundations of knowledge or probability. This I call argumentum ad judicium. This alone of all the four types of arguments, brings true instruction with it, and advances us in our way to knowledge. (Locke [1690], Vol. 2, pp. 411)
The following explanation shows that this validity is derived not only from the activity of judgment but also from “the things themselves”:
[Truth] must come from proofs and arguments, and from light arising from the nature of things themselves. (Id., pp. 411-412).
Thus, the ad judicium reasoning is based on « the foundations of knowledge or probability », that is, scientific criteria, and develops an object-based knowledge. In any case, this mode of reasoning excludes the passions and distrusts the speech, see ornament and argument.
Strictly speaking, ad judicium is not an argument scheme in itself, but rather encompasses the entire scientific methodology. It follows from Locke’s definitions, that the correct argumentation for social questions and human projects is the name of scientific method when applied to social questions and human projects.
Ad ignorantiam, ad hominem and ad verecundiam arguments also appeal to judgment, or at least to calculations based on the speaker’s knowledge. Ad ignorantiam is based on an evaluation of the pros and cons of competing claims. Ad hominem appeals to consistency, while ad verecundiam is based on a feeling of personal modesty or inadequacy, which may or may not be well-founded. Nevertheless, these arguments are considered fallacious because they are subjective. Subjective here does not mean “arbitrary”, but rather non-universal, and context-dependent, taking into account the circumstances of the discourse situation and the speaker’s transient state of knowledge.
This conception of argument is the antithesis of what Grize calls « a logic of subjects », see schematization
2. Ad judicium, a polysemic label
Various non-equivalent, definitions are attached to the ad judicium label. This can be somewhat confusing.
(1) Perhaps referring to Locke, Whately thinks that the label ad judicium designates “most likely the same thing” as the ad rem argument ([1832], p. 170), i.e., an argument to the matter, or to the thing itself. This identification is based on Locke’s belief that true knowledge is derived “from the nature of things themselves” (see above).
In this case the terminology would simply be redundant, which is relatively harmless.
(2) A dictionary of theology defines ad judicium as: “an argument that appeals to common sense and general opinion to support a position”[1]. This definition is quite different, and completely opposed to Locke’s perspective, if we consider his positions on rhetoric, see ornamental fallacy.
(3) Bentham uses the term ad judicium to refer to several fallacies of confusion (Bentham [1824]), see political arguments: two collections.
The terminological and conceptual field covered by the label ad judicium can thus be arranged as follows:
— In Locke’s sense, it is scientific reasoning, based on things.
— In Whately’s sense, it is an argument on the merits of the case similar to ad rem.
— In theology, it is an argument based on the consensus of nations.
— In Bentham’s sense, the ad judicium fallacies are maneuvers that obstruct sound judgment.