Conventions are ubiquitous in human life. Conventions are certain regularities in human actions and interactions, such as commonly observed practices, customs, and traditions. Conventions also reflect the less observable, namely, the underlying beliefs and implicit theories about the world that people come to share. They are often taken as conventional wisdom or common sense. What is attempted in the chapter is an exploration of conventions as knowledge commons; conventions will be presented as the necessary consequence of the human predicament of decision making in the face of uncertainty given the human ability to imagine, learn and communicate. The exploration of the nature of convention attempted here turns upside down the theory of the dominant tradition in economics, focusing on the logic of choice, taking as given the ends and means. Instead, we take the logic of choice as given (as non-problematic) and focus on how human beings cope with uncertainty (with the knowledge problem).