Thus, the emergence of neoclassical economics in the nineteenth century was very much influenced by Newtonian and Cartesian physics, moving from qualitative analysis to quantifying human behavior by assuming rational behavior and excluding uncertainty. This “predetermined equilibrium” thinking – reflected in the view that markets always self-correct – led to policy paralysis until the Great Depression, when John Maynard Keynes’s argument for government intervention to address unemployment and output gaps gained traction.