The idea of working in sympathy with a horse in order to obtain cooperation is not new, with documented instances as far back as the two part treatise "On Horsemanship" by Xenophon (c. 430 – 354 BCE), which amongst other points, emphasized operant conditioning and emphasized reassurance over punishment. Later classical dressage practitioners such as Antoine de Pluvinel (1555–1620 CE) and François Robichon de La Guérinière (1688–1751) also emphasized gentle techniques. However, gentle training methods have always had to compete with harsher methods, which often appear to obtain faster, but less predictable results. In particular, the cowboy tradition of the American west, where the economics of needing to break large numbers of semi-feral horses in a short period of time led to the development of a number of harsh training methods that the natural horsemanship movement specifically has set out to replace.