Three of the main battlegrounds between historians concerning the Industrial Revolution have been over the speed of the transformation, the key reason(s) behind it, and even whether there really was one. Most historians now agree that there was an industrial revolution (which is a start), although there has been discussion over what exactly constitutes a 'revolution' in industry. Phyliss Deane described an ongoing, self-sustaining period of economic growth with large generational increases in productivity and consumption.
If we assume there was a revolution, and leaving speed aside for the moment, then the obvious question is what caused it? For historians, there are two schools of thought when it comes to this. One looks at a single industry triggering a 'take off' among the others, while a second theory argues for a slower, longer-term evolution of many interlinked factors.
Cotton's Take Off
Historians like Rostow have argued that the revolution was a sudden event stimulated by one industry surging ahead, dragging the rest of the economy along with it. Rostow used the analogy of an airplane, 'taking off' the runway and swiftly rising high, and for him-and other historians-the cause was the cotton industry. This commodity grew in popularity during the eighteenth century, and the demand for cotton is seen to have prompted investment, which stimulated invention and in turn improved productivity. This, the argument goes, stimulated transport, iron, urbanization, and other effects. Cotton led to new machines to make it, new transport to move it, and new money to be spent on improving the industry. Cotton led a massive change in the world but only if you accept the theory. There is another option: evolution.
Historians such as Deane, Crafts, and Nef have argued for a more gradual change, albeit over different time periods. Deane claims that gradual changes in a multitude of industries all occurred simultaneously, each subtly stimulating the other further, so the industrial change was an incremental, group affair. Iron developments allowed steam production which improved factory production and long distant demand for goods provoked investment in steam railways which allowed greater movement of iron's materials.
Deane tends to put the revolution as starting in the eighteenth-century, but Nef has argued that the beginnings of the revolution can be seen in the sixteenth and seventeenth centuries, meaning it may be inaccurate to speak of an eighteenth-century revolution with preconditions. Other historians have seen the revolution as a gradual, ongoing process from before the traditional eighteenth-century date right up until the present day.