Classical economics is generally agreed (but see section Debates on the definition of classical economics below) to have developed into neoclassical economics – as the name suggests – or to at least be most closely represented in the modern age by neoclassical economics, and many of its ideas remain fundamental in economics. Other ideas, however, have either disappeared from neoclassical discourse or been replaced by Keynesian economics in the Keynesian Revolution and neoclassical synthesis. Some classical ideas are represented in various schools of heterodox economics, notably Georgism and Marxian economics – Marx and Henry George being contemporaries of classical economists – and Austrian economics, which split from neoclassical economics in the late 19th century.