Given the technological feasibility of this branch of economic activity in late Hanoverian Scotland, wouldn't it be sensible to maximise grape output and to produce as much wine as possible? Indeed, wouldn't it be "reasonable", as he noted, "to prohibit the importation of all foreign wines to encourage the making of claret and burgundy in Scotland?" The point is that, because resources are finite, the maximisation of one kind of output implies the loss of others. If Scotland's available labour and capital had been wholly committed in 1776 to wine-making, its production of oats and barley and of linen and whisky would have been much lower.

Smith conjectured that the cost of obtaining Scottish wine from glasses, hotbeds and hot walls might be "about thirty times the expense for which at least equally good [wines] can be brought from foreign countries". The answer was for Scotland to allocate three units of resources to making whisky and to exchange whisky for wine, leaving 97 units of resources available for other purposes. By comparison, putting all 100 units of resources into the making of wine was barmy. Both the notion of "producing as much as possible" and the word "maximisation" are deceitful. They rely on the premise that "we" as a nation are not pulling our weight and doing enough to engineer food production. But the economic problem is about resource allocation, not engineering. The issue is not "how do we produce as much food as possible?" but "how should scarce resources be split between different kinds of food output?"

Mr Benn's difficulty is that resources employed in farming have alternative uses. Although the maximisation of food production may be the alpha and omega of his policy-making team in Whitehall, what is to be said about that holy of holies of other Labour politicians, the maximisation of manufacturing production? Has it been forgotten that in the late 1990s, New Labour revered the output of Cool Britannia's creative industries?