The virtue of understanding the world in order to effectively live in it.

This virtue consists of using your reasoning abilities to learn about the world, attain knowledge, and using it in the pursuit of values. In order for any action to be effective, it must be properly based on the facts of reality. Rationality is critical to any pursuit of actions, because without it, your actions would become pointless.

Rationality also consists of using logic to make sense of what you learn. It involves using objectivity to keep your ideas consistent with the truth. It involves avoiding fictions, lies, arbitrary beliefs, and evasions. It involves understanding and clarity, and avoid letting your emotions cloud your thoughts.

Rationality also consists of developing the skills to acquire and use that knowledge. Your ability to learn new things is important. So is your ability to analyze new and old information. Your mind has many tools it uses to properly deal with reality, and the virtue of rationality encourages the strengthening of those skills. It also encourages the actual learning of new ideas. If understand reality is useful in achieving values, the more you know, the better off you'll be.