Enigma #1: Why did Adam Smith become a Commissioner of Scottish Customs in 1778?

Following up on my recent series on “Walter Bagehot and Adam Smith”, I have decided to write up a new series of blog posts devoted to the many puzzles or paradoxes about the Scottish philosopher’s life and work that remain open to this day, beginning with Smithian Enigma #1: Adam Smith’s surprising decision (surprising to us, at least) to become a Commissioner of Scottish Customs in 1778. To the point, why did a bookworm and scholar like Smith decide to give up his intellectual pursuits (for the most part) in order to become an anti-trade, pro-protectionist bureaucrat for the remainder of his life? A review of the relevant scholarly literature (see, for example, here and here) reveals several possible reasons or motives:

1. Financial security. One possibility, perhaps the simplest and most plausible one, is that Adam Smith, who would reach the ripe old age of 55 in 1778, was enticed by the pecuniary aspect of the position of commissioner — i.e. a position that paid 600£ per annum, or double the amount of Smith’s annual pension from the 3rd Duke of Buccleuch and quadruple his previous salary as a professor of moral philosophy. (See Anderson, Shughart II, & Tollison, 1985, p. 751, who credit Walter Bagehot, 1876, p. 38 with this theory.) On this view, Smith was simply trading off his scholarly pursuits for financial security.
2. Regulatory sabotage. Another possibility is that Smith was a “free trade saboteur”, so to speak — i.e. that Smith became a commissioner in order to infiltrate the inner sanctum of the Customs Office and implement his intellectual agenda by nudging government policy toward free trade. (See again Anderson, Shughart II, & Tollison, 1985, p. 751, who attribute a more watered-down version of this theory to E. G. West, 1976, pp. 126-128.) Alas, not only is there no evidence that Smith engaged in regulatory sabotage; on the contrary, all the available evidence shows that Commissioner Adam Smith prosecuted smugglers to the full extent of the law and energetically enforced protectionist policies during his tenure as commissioner!
3. Pragmatic accommodation. Yet another possibility is that there is no enigma to see here, that Smith was, in fact, a realpolitik pragmatist who did not really believe in or take literally his own free trade/limited government rhetoric. (See once again Anderson, Shughart II, & Tollison, 1985, p. 751, who cite Jacob Viner, 1966, p. 144, pp. 150-151, as well as T. D. Campbell & Ian Simpson Ross, 1981, pp. 87-88, for this proposition. See also Book 5 of Smith’s Wealth of Nations, which can be read as a ringing defense of strong central governments.) Alternatively, a more charitable interpretation is that Smith may not have fully appreciated the ultimate and unavoidable conflict between his free trade and “natural liberty” rhetoric and his defense of limited government when he first wrote his magnum opus.
4. Scholarly fatigue. Last but not least, Gary Anderson, William Shughart II, and Robert Tollison (1985, p. 752) themselves offer their own preferred theory as to why Smith became a bureaucrat: “the most plausible explanation for Smith’s choice of the commission is simply that he was tired of scholarly work.” Later, Anderson, Shughart II, & Tollison add that Smith was not only “tired of economics and scholarship” but that he also “found his work at customs satisfying and interesting” (p. 757). Alas, considering that Smith was a lifelong bookworm who later made substantial revisions to both of his great works while he was still a commissioner (namely, to the 3rd edition of The Wealth of Nations, published in 1783, and to the 6th and last edition The Theory of Moral Sentiments, published in 1790), this last conjecture is improbable at best.

So, which of these four hypotheses is most likely to be true? Perhaps, in some form or another, all of them? And more generally, in the realm of historical conjecture, how does one decide which theory or possibility is most likely to be true? Stay tuned; I will proceed to “Smithian Enigma #2” in my next post …