AD JUDICIUM Argument

• Lat. iudicium, “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 holds to be valid, with types of argument,  that he holds to be fallacious: the arguments ad ignorantiam, ad hominem and ad verecundiam (Lat. verecundia, modesty); S. 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, 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 light arising from the nature of things themselves. (Id., p. 411-412).

Thus, the ad judicium reasoning is 1) based on “ the foundations of knowledge or probability”, that is, scientifc criteria, and 2) 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 encompasses the entire scientific methodology. It follows from Locke’s definitions, that the correct argumentation 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 upon the speaker’s states of knowledge. Ad ignorantiam is based on an evaluation of the proof pro and contra of the various claims in competition;   ad hominem appeals to consistency; ad verecundiam is based on a feeling of personal modesty or inadequacy, which may or may not be well-founded. Nevertheless, they are considered fallacious because they are subjective. Subjective here does not mean “arbitrary”, but rather non-universal, context-dependent, taking into account the circumstances of the discourse situation and the speaker’s transient state of knowledge.
Argument thus conceived is the antithesis of what Grize calls « a logic of subjects », S. 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 the fact that Locke thinks 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] which is something quite different, and completely opposed to Locke’s perspective, if we consider his positions on rhetoric, see Ornamental fallacy.

(3) And Bentham uses the label ad judicium to designate a number of 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 scientific reasoning, based on things.
— In Whately’s sense as for ad rem, an argument on the merits of the case.
— In theology, an argument based on the consensus of nations.
— In Bentham’s sense, the ad judicium fallacies are maneuvers which tend to obstruct the sound exercise of judgement.