Until recently, 'Subjective Expected Utility Theory' was accepted within the economics profession as the theory of rational decision-making under risk and under certainty. However, its pre-eminence in recent years has been undermined as a consequence of a flood of experimental evidence casting doubt on its descriptive accuracy. This book documents the theoretical reconstruction of the theory of decision-making in the aftermath of this flood. It is divided into three parts and contains the key papers introducing and describing new theories of decision under risk, new theories of decision under uncertainty and new theories of dynamic decision-making.