Marx on economic development

From The Germany Ideology (1846), critiquing other social thinkers of the time who saw “liberation” as a purely philosophical question:

Nor will we explain to them that is only possible to achieve real liberation in the real world and by employing real means, that slavery cannot be abolished without the steam-engine and the spinning-jenny, serfdom cannot be abolished without improved agriculture, and that, in general, people cannot be liberated as long as they are unable to obtain food and drink, housing and clothing in adequate quality and quantity.  ‘Liberation’ is a historical and not a mental act (p. 169).

Presages the Lewis-Ranis-Fei model of agricultural productivity by a good century.