This issue of JHET marks the end of one era and the beginning of another. Don Walker, the only editor that JHET has ever had, has stepped aside after 9 years on the job. Under Don's guidance, JHET developed into a highly respected outlet for scholarship in the history of economic thought, to the point where the supply of high quality submissions prompted the move to quarterly publication in 1988. His labors on behalf of the Journal stretched well beyond the standard editorial function: he handled or oversaw all aspects of the physical production of the Journal, the mailing of the Journal, and numerous other messy details that the present editor has the luxury of passing off to Carfax (that, too, largely owing to Don's efforts).

In order that this essay may be clear to the reader, some understandings about terminology must be established. First, if we speak of “theories that were formulated in the past,” ordinarily we mean to leave open the question of whether they are still valid, and if we speak of “past theories,” ordinarily we imply that they have been discarded and that implies that they were defective and were supplanted by current theories. Nevertheless, in this essay the latter term, used for the sake of brevity, will have the same meaning as the former expression. If a past theory is considered to be invalid, that will be staled explicitly.

It is well known that the General Theory contains only one diagram, this occurring in chapter 14 criticising the orthodox theory of the rate of interest. Attached to the diagram is a footnote containing an acknowledgement: “This diagram was suggested to me by Mr. R.F. Harrod” (CW VII, p. 180). The impression conveyed by this remark is that Harrod drew the diagram and offered it to Keynes, who then accepted and used it. Further enquiry into the diagram's origins reveals the existence of an initial version which grew out of correspondence between Keynes and Harrod in August-September 1935 (CW XIII, pp. 526-63). Two of Harrod's writings–his (1951) Keynes biography and a letter to Hawtrey in 1951–imply that he was the author of the initial version, and that this was essentially the same as the published version. And, in seeming corroboration of Harrod's comments, there is the virtual equivalence of the initial version given in The Collected Writings of John Maynard Keynes (CW XIII, p. 557) and the final version printed in the General Theory (CW VII, p. 180J. Taken individually and collectively, these items of evidence all point in the same direction. They support the reasonable inference that, apart from trivial changes in lettering, Harrod was the sole author and creator of the initial and final versions of the diagram, and that Keynes was merely the recipient.

Roy Harrod (1951, p. 453) explicitly states that he “supplied a diagram purporting to reconcile the classical theory [of interest] with [Keynes's] theory, and he incorporated it in the [General Theory]-the only diagram in it!” (italics added). John M. Keynes (1936, p. 180n) himself writes: “This diagram was suggested to me by Mr. R.F. Harrod.” Furthermore, Harrod, in a letter to Ralph Hawtrey (19 June 1951) also says: “I was myself responsible for the diagram on page 180 which was an attempt to demonstrate to Maynard that his theories were not quite so out of line with the classical position as he supposed” (quoted in Warren Young 1987, p. 136). Now Rod O'Donnell (1999) claims that Harrod never supplied a diagram but only suggested how one could be drawn. Thus both Harrod and Keynes have misled us about the genesis of the only diagram in the General Theory. O'Donnell advances arguments in support of his claim which do not appear convincing.

To declare my case “not proven” is irrelevant. I agree my case is not proven, but all other cases on this topic, including Ahiakpor's, are equally unproven. Arguing about proof here is a waste of time. We simply do not have enough data for deductive certainty or even for the less stringent criterion of “proof beyond reasonable doubt.” The written record is not conclusive and the protagonists are dead. What is not a waste of time, however, is discussing probabilistic inferences from incomplete evidence.

Although this essay is essentially an intellectual biography, personal experiences have influenced my career as an economist and historian of economic thought. For this reason, I shall devote some space to these experiences before turning to the main topic.

My parents migrated from Sicily to the United States prior to the First World War; met and then married in this country and eventually settled in Hartford, Connecticut. I was conceived in 1929, the year of the Great Crash and born the following year at the onset of the Great Depression. However, for my family our economic depression had begun in 1929, when my father was seriously injured at a construction site and spent the next 8 months hospitalized, leaving my mother, who was pregnant with me, and my two siblings, without any means of support.

More than 100 years have passed since Alfred Marshall introduced the representative firm to economic theory in 1891. During this long period of time, many arguments have been raised giving either support or opposition to the concept. In recent years, macroeconomists have taken an increasing interest in the representative firm. Since the beginning of the modern microfoundations literature in the early 1970s, the representative firm and its big brother, the representative agent, have been made essential analytical tools for linking macroeconomics and microeconomics. Within this debate, the microfoundation of business cycle theory has played a prominent role.

Adam Smith starts his account of economic life supposing two trading individuals, and not with Robinson Crusoe alone on an island. It is a consequence of this modeling strategy that, when considering an actor's choice, the model builder automatically has access to the judgment of the spectator. Thus it is that when Smith describes the actor gambling for money, he takes into consideration the fact that the spectator will make note of unusual events. In particular, the winner of a large-number lottery will become famous. To the extent that fame is desired, the actor's decision will be influenced by the spectator's judgment. The gambling model Smith describes is an exchange between the actor–who takes risk–in return for the chance of applause from the spectator. Everything in Smith's account is an exchange; hence, we denote Smith's model as a katallactic model, thus remembering Richard Whately's suggestion to rename political economy as the science of exchange, from the Greek καταλλατειγ–to exchange.