There has been a twentieth century school of economic thought that has been enormously influential especially in microeconomics.
Neoclassical economists share the following points in common.
Almost all neoclassical economists are positive economists. Neoclassical economists believe that free markets usually bring about an efficient allocation of resources. Conversely, efficient allocation is the important thing about free markets. Another thing neoclassical economists share is some assumptions that they make as a starting point. Many other economists accept those assumptions as well, but there is also some controversy about them.