This chapter positions rationality as a democratic principle, tracing its evolution from Aristotle’s human capacity for reason to Weber’s value-oriented vs. goal-oriented action to Habermas’s communicative rationality and other modern conceptions. It then presents critiques of rationality, such as how it can be used to lead to dehumanization, as well as how it reflects Western-centric thinking. The chapter describes bounded rationality, recognizing the inability to guarantee absolute certainty, where truth and reason are interactive and public. To ensure ethical action, it requires recognition of fallibility as well as a critical spirit to navigate potential pitfalls of instrumental deployment. This positions rationality as a useful tool that contributes to and supports a pluralistic civic society.