In theory, capitalism is at least as old as Adam Smith's Wealth of Nations. William Bernstein would probably argue that capitalism, in theory, dates back to Henry Martyn's 1701 pamphlet entitled Considerations on the East India Trade.
Some would argue that capitalism started on the macro-level with the repeal of the Corn Laws in England, and I guess that's what we are talking about: capitalism on the macro-level. Capitalism on the micro-level must surely have existed since the first exchange between humans took place.
If that was the beginning of capitalism on the macro-level, when did it's end occur?
Of course, I have my own ideas for the answers to these questions, but I thought I would ask here.
Read my Nolan Chart column "Me & My Big Mouth"
Capital is an industrial organization, large-scale capital ownership and wage labor to operate this capital, resulting in enormous productivity increases that were not possible in agrarian or feudal societies.
It's not a theory.
The fallacies of intellectual communism, a compilation - On the nature of power
I like this, from the OED:
1642 H. PARKER Vintners Answer 23 The Vintners might bargain at pleasure, they had an open and free market, and commonly they bought under the prices set, and they pleased themselves with a free choice.