Human thinking and reasoning can be compared with a ‘normative’ standard—a formal theory of right and wrong answers. The normative theories mostly applied are decision theory, probability theory, and logic. People frequently make errors by these standards and have been shown to have many cognitive biases. Does this mean that human beings must be intrinsically irrational? ‘Are we rational?’ considers different definitions of rationality: instrumental, epistemic, bounded, normative, ecological, and evolutionary rationality. It also asks how important is general intelligence in rationality? More recent psychological research suggests that both instrumental and epistemic rationality, defined by conventional means, are aided by a combination of general intelligence and rational thinking disposition.