This article argues that the field of asset pricing theory is undergoing a scientific revolution in Kuhnian terms. The orthodox view is one of determinate change in causal processes and inherent stability whereby financial markets, left unfettered, allocate nearly perfectly society's scare capital. However, decades of mounting anomalous evidence against the implications of stable causal processes perpetuated by conventional models based on efficient markets and the rational expectations hypothesis have paved the way for alternative avenues of research. Although various approaches (...) are being developed, the imperfect knowledge economics class of models has emerged as a potential new paradigm in the field of macro-finance. By stopping short of fixing in advance the specification of individual forecasting behavior and the causal process, the IKE class of models has been able to reconcile many of the puzzles found within the literature on asset price behavior and risk. (shrink)