Say's Own Law (1814)

Mu"nchau in the FT suggests: 'It is that official economic thinking in Paris has not progressed in 211 years.' He clearly refers to the first edition of Say's Treatise (1803). Baumol (Economica 1977) has plausibly argued that Say's Own Law only appears in the second edition of 1814, stating that in the long run, demand will be able to keep up with enormous increases in output. This may seem a truism today, but it was a burning question at the beginning of the Industrial Revolution.
My recent Say biography 'Revolutionary, Entrepreneur, Economist (Routledge 2013)' corroborates Baumol's interpretation by quoting from Say's correspondence with his relative Michel Delaroche. Say asks his comment on the manuscript version of 'a chapter containing very fundamental matters ... too imperfectly discussed in my first edition.'
And in another letter: 'If such a chapter would be generally recognised, people would know the origin of one of the causes of the present lack of sales, and of the one threatening us. ... What an indignation people would feel if they knew the entire present misfortune.'
Official economic thinking or not, this dates back exactly two centuries, not 211 years.

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