Reply to Dewsbury on "On Misrepresenting Lloyd Morgan's Canon: Comment on Thomas"

Roger K Thomas

University of Georgia

Athens, GA

It is regrettable that Dewsbury (2002) wrote:

Thus, I stand by my statements of the last 20 years or so that Thomas quoted [as examples of misrepresentations of Morgan's canon], including [my] brief statement of 2000 "In his classic textbook, Morgan (1894) outlined his famous canon that an animal's behavior should be interpreted in terms of the PSYCHOLOGICALLY SIMPLEST PROCESSES consistent with the data. Morgan's canon, AND ITS RELATED CONCEPT, PARSIMONY, spread widely during the period" (emphasis added), and my 1984 statement "the law of parsimony and Morgan's canon are two CLOSELY RELATED principles" (p. 188). [Bold print was used here and below merely to denote that they are quotations.]

That is regrettable because, in doing so, Dewsbury will continue to misrepresent Morgan's canon by confounding his interpretation of Morgan's canon with Morgan's intentions (see Thomas, 2001).  As I stated in my paper:

It was deemed appropriate to include an author...[as an example of one who misrepresented Morgan's canon] when that author associated Morgan's canon with Ockham's razor, the law of parsimony, or a simplicity criterion or represented Morgan's canon as being anti-anthropomorphic or anti-anecdotal, if that author did so without negating the association with regards to Morgan's intentions or did so without acknowledging any of the history of misrepresentation in conjunction with such associations. [Italics in the original]

It is acceptable, even expected, that scholars will re-interpret, re-construct, de-construct, assess, and re-assess historical information, but should not such activities, especially by historical scholars, begin with as accurate a presentation of the facts as is reasonably possible?  In this case, the facts under scrutiny are those associated with Morgan's canon and what Morgan meant when he wrote it.  Morgan's canon, as he intended it and despite what others may say, did not advocate a simplicity criterion.  Dewsbury's insistence on representing Morgan's canon as indicated above might be a relatively minor matter were it not for the documented extensive history of such misrepresentations together with the documented extensive history of efforts (some vigorous) to correct such misrepresentations (see Thomas, 2001).  Considering those histories, to continue any representation of Morgan's canon without distinguishing Morgan's views from Morgan's interpreter's views misrepresents Morgan's canon. 


Morgan made a considerable effort in his discussion of the canon to dissociate it from a simplicity as a criterion to be used in formulating or choosing between alternative interpretations or processes (Thomas, 2001, 2002).  I might agree with Dewsbury if he said that it was not unreasonable for Morgan's interpreters to see a relationship, even a close one, between Morgan's canon and a simplicity criterion (including parsimony), especially if those interpreters had not read what Morgan wrote about "parcimony" elsewhere (viz., Animal Life and Intelligence, 1891; see Thomas, 2001).  Unlike "simplicity" which Morgan (1894) explicitly addressed in conjunction with the canon, he did not explicitly address "parsimony" in his efforts to clarify the canon, although Dewsbury implied that he did (see Dewsbury's paragraph beginning, "Here Morgan is showing is exactly....").


Dewsbury (2002) also wrote, "Basically, I think we are really quibbling over the use of a couple of words."  Our differences are deeper and more fundamental.  Any resolution of our differences must begin with distinguishing clearly between Morgan's intentions regarding Morgan's canon and others' attributions of intentions to Morgan regarding Morgan's canon.  As far as re-interpreting and applying Morgan's canon in contemporary psychology, our differences also run deep and stem from our significantly different opinions regarding the validity, utility, definability, and applicability of simplicity (or parsimony) as a criterion for choosing between explanations or between psychological processes


Interested readers are encouraged to consider carefully and critically what I have written about Morgan's canon (Thomas, 1998, 2001, 2002), what Dewsbury has written (Dewsbury, 2002 and citations of Dewsbury in Thomas, 2001), and what Morgan (1891, 1894) has written that bears on the canon at the time he wrote it.



NOTE: Any references cited above and not listed here may be found in Thomas (2001).

Dewsbury, D. A. (2002). On Misrepresenting Lloyd Morgan's Canon: Comment on Thomas. History & Theory of Psychology Eprint Archive,

Thomas, R. K. (2001). Lloyd Morgan's Canon: A History of Misrepresentation. History & Theory of Psychology Eprint Archive,

Thomas, R. K. (2002). Reply to Black and Wozniak on "Lloyd Morgan's Canon: A History of Misrepresentation." History & Theory of Psychology Eprint Archive,