Rick Grush (1993) Van Brakel's Position is Perfectly Coherent. Psycoloquy: 4(24) Frame Problem (8)

Volume: 4 (next, prev) Issue: 24 (next, prev) Article: 8 (next prev first) Alternate versions: ASCII Summary
PSYCOLOQUY (ISSN 1055-0143) is sponsored by the American Psychological Association (APA).
Psycoloquy 4(24): Van Brakel's Position is Perfectly Coherent

Commentary on Fetzer on van Brakel on Ford & Hayes on the Frame Problem

Rick Grush
Department of Philosophy
University of California, San Diego
La Jolla, CA 92037



Fetzer's reasons for disputing van Brakel's (1992) position are based on misunderstanding of van Brakel's arguments.


Frame-problem, artificial intelligence, temporal logics, independent persistence, attention, Hume, dynamic frames, qualification problem.
1. Fetzer (1993) claims that there are three reasons for disputing van Brakel's (1992) position. However, all three of the putative reasons are results of Fetzer's misunderstanding of van Brakel's position, or of simple misunderstanding.

2. As Fetzer points out, "Van Brakel claims that there are three dimensions to the frame problem: [A] Which things change, and which don't? [B] How can [A] be represented? and, [C] How can/do we reason about [A]?" Van Brakel denies that the frame problem is the problem of induction in disguise, but admits that aspect [A] of the frame problem is "related" to the problem of induction. Even if one agrees with Fetzer that [A], [B] and [C] are all intimately interrelated (which seems reasonable) it does not follow, as Fetzer claims, that van Brakel's position "is not logically consistent." It is clearly possible for X to be related to Y without it being the case that X is Y in disguise -- for example, if the relation in question is a part/whole relationship (which is clearly what van Brakel has in mind).

3. The second objection Fetzer aims at van Brakel seems, on my reading of Fetzer's text, to be a thicket of confusions.

3.1. Fetzer states that "in maintaining that the frame problem is a special case of the problem of induction, not only do I not deny that it has other dimensions (of representation and of implementation) but I actively affirm it." The only sense I can make of this statement is that it is a response to van Brakel's claim that "philosophers tend to concentrate on [A]." But unless "concentrate on [A]" is glossed as "maintain the irrelevance of all non-[A]," which is at best an uncharitable reading, Fetzer has no need to defend himself here, as there is no attack. In fact, given van Brakel's list of aspects of the frame problem (van Brakel, 1992, 1.4) and Fetzer's broad conception of induction, the dispute here seems to be one not about the nature of the frame problem, but about the extension of the phrase "problem of induction."

3.2. Fetzer continues: "Surely, if there is no answer to question [A] then there are no answers to [B] or [C], whose solutions presuppose a solution to [A]. Thus, in denying my position, van Brakel denies his own." This seems to be motivated by an ambiguity in the phrase "denies my position." If "denies Fetzer's position" means "denies that induction plays a role in [A]," then Fetzer is right to claim that denying his position would put van Brakel in a difficult spot. But van Brakel does not deny Fetzer's position in this sense. Rather, he denies Fetzer's position in the sense that he denies that "the problem of induction is ALL THERE IS to [A]," and this lands van Brakel in no difficulty, given his narrower conception of the problem of induction.

4. In Section 3 of Fetzer's commentary, he claims that van Brakel asserts "that it is impossible to give necessary and sufficient conditions for the occurrence of an event of the definition of a concept."

4.1. But van Brakel says no such thing. What he says is (van Brakel, 2.2) "it is, in general, not possible to specify the necessary and sufficient conditions for something." The force of "in general" is cashed out by van Brakel's admission that conventional definitions for the use of certain words, or physical laws WITH CETERIS PARIBUS CONDITIONS HOLDING may be amenable to such necessary and sufficient conditions. Curiously, Fetzer offers, as counterexamples to van Brakel's claim, the example of the definition of a bachelor and the lighting of a match (in terms of necessary and sufficient conditions), both of which are ALLOWED by van Brakel.

4.2 Ironically, it is Fetzer who seems to contradict himself within a single sentence. He states, concerning the striking of matches in appropriate conditions (Section 4): "The latter conditions [the striking of the match with oxygen present, etc.] appear to be individually necessary and jointly sufficient to bring about an occurrence of the kind described by the former [the match lights], although other causes are of course possible." Well, if OTHER causes are in fact possible, then the causes mentioned are not in fact necessary: Fetzer is in effect saying "X is necessary and sufficient for Y, though of course some non-X may be sufficient" which is to say "X is necessary for Y, and X is sufficient for Y, and X is not necessary for Y." A more charitable reading (barely sanctioned by the text) is that Fetzer is simply pointing out the necessity of taking cognizance of the appropriate ceteris paribus conditions. But if this is the right reading, then it is not clear where the disagreement between he and van Brakel is.

5. I think there is actually less disagreement between van Brakel and Fetzer than Fetzer makes out, at least on these issues. The heart of the misunderstanding, it seems to me, stems simply from disagreement over what is covered by the phrase "problem of induction," plus a few unfortunate misreadings.


Fetzer, J.H. (1993) Commentary on van Brakel on Ford & Hayes on the Frame-Problem. PSYCHOLOQUY 4(14) frame-problem.4

Ford, K.M. and P.J. Hayes (1991) Reasoning Agents in a Dynamic World: The Frame Problem, Greenwich: JAI Press.

Hayes, P.J. (1992) Summary of "Reasoning Agents in a Dynamic World: The Frame Problem" (Ford & Hayes 1991, Eds.) PSYCOLOQUY 3(59) frame-problem.1

van Brakel, J. (1992) The Complete Description of the Frame Problem. PSYCOLOQUY 3(60) frame-problem.2

Volume: 4 (next, prev) Issue: 24 (next, prev) Article: 8 (next prev first) Alternate versions: ASCII Summary