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Reasoning about change: time and causation from the standpoint of artificial intelligence
Shoham Y., MIT Press, Cambridge, MA, 1988. 200 pp. Type: Book (9780262192699)
Date Reviewed: Jan 1 1989

The main part of this dissertation is the development, in several stages, oflogical formalisms for expressing issues related to situations involvingseveral items that react with one another over a period of time. Thisfield of interest is illustrated in terms of scenarios involving rollingand colliding billiard balls. A later section discusses causation as anadditional issue of these formalisms.

To this reviewer the decisive issue in this presentation is the startingpremise--the assumption that significant insight into the events takingplace when solid bodies, such as billiard balls, move about can be obtainedsolely by calculations with truth values, that is, by reasoning. Thisessential assumption becomes evident on page 9, where it is suggestedthat, in dealing with moving objects, “precise numerical information(such as the precise distance between two billiard balls) is unnecessaryand unavailable.”

It seems to this reviewer astounding, indeed appalling, that at this timein history, 300 years after Newton, such a view of motions and mechanicscan be entertained. How can anyone dealing at all seriously with time andmotion be unaware that the motions of the heavenly bodies, including theirencounters in eclipses, are calculated very successfully as a matterof astronomical routine, and that the motions of aircraft are beingcalculated continuously in airport control systems, to mention just twoexamples. How can anyone present one hundred pages of formalism in orderto arrive at a non-solution of the problem solved with high efficiencyby Newtonian mechanics? For despite the author’s claims about its efficiency,what emerges after these hundred pages is a non-solution.

Causation, the second issue taken up by the author, fares no better thanmechanics. The author quotes seven lines from Bertrand Russell’s discussionof cause, which establishes quite clearly that causes have no place inphysics and astronomy, but then joins several other authors who quoteRussell without grasping his message. It occurs to none of these authors thatmeaningful talk of causes, like meaningful talk of anything else, is amatter of context and situation. A typical context and situation would bethat of a serviceman being called in to fix a broken television receiver.The cause here might be a defective line cord, for example. Spelled out inmore detail, the context is that of a person dealing with a thing involvingseveral issues or parts, which are intended by the person to serve aparticular function. The situation is that the thing fails in itsintended function, and we are then entitled to ask for the cause of thefailure.

It is meaningful to ask why something fails to function according to ourintent. To ask why something functions properly makes no sense, sincethe circumstances that lead to the present situation of the world are beyondenumeration. In the book under review this latter notion gives rise towhat is called the frame problem. The reader is misled by this euphemisminto expectin g that it will be solved. It will not.

It is a sad reflection on the state of computer science that the presentwork can not only be published as a book, but be accepted as a Ph.D.dissertation by Yale University. It has no merit.

Reviewer:  P. Naur Review #: CR125961 (89010011)
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Deduction And Theorem Proving (I.2.3 )
 
 
Knowledge Representation Formalisms And Methods (I.2.4 )
 
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