The concept of dual rationality in human agents is well understood. It is significant in the work of the economist and Nobel Laureate Friedrich Hayek. In psychology Sigmund Freud described 'dual information processing'. More recently in cognitive science Daniel Levine has extensively studied the dual mechanisms in the human brain that handle these two forms of rationality. It is perhaps surprising that work in artificial intelligence has focussed heavily on Cartesian constructivist rationality (particularly on game theory, decision theory and logic) as humans deliberate using models based on reason for only a minute proportion of the decisions that they make. This paper aims to open discussion on ecological rationality in artificial, computerised agents, and to examine some of the issues in designing ecologically rational agents.