Second, there is courage. The obvious form of intellectual courage is the willingness to hold unpopular views. But the subtler form is knowing how much risk to take in jumping to conclusions. The reckless thinker takes a few pieces of information and leaps to some faraway conspiracy theory. The perfectionist, on the other hand, is unwilling to put anything out there except under ideal conditions for fear that she could be wrong. Intellectual courage is self-regulation, Roberts and Wood argue, knowing when to be daring and when to be cautious. The philosopher Thomas Kuhn pointed out that scientists often simply ignore facts that don’t fit with their existing paradigms, but an intellectually courageous person is willing to look at things that are surprisingly hard to look at.

Third, there is firmness. You don’t want to be a person who surrenders his beliefs at the slightest whiff of opposition. On the other hand, you don’t want to hold dogmatically to a belief against all evidence. The median point between flaccidity and rigidity is the virtue of firmness. The firm believer can build a steady worldview on solid timbers but still delight in new information. She can gracefully adjust the strength of her conviction to the strength of the evidence. Firmness is a quality of mental agility.

Fourth, there is humility, which is not letting your own desire for status get in the way of accuracy. The humble person fights against vanity and self-importance. He’s not writing those sentences people write to make themselves seem smart; he’s not thinking of himself much at all. The humble researcher doesn’t become arrogant toward his subject, assuming he has mastered it. Such a person is open to learning from anyone at any stage in life.

Fifth, there is autonomy. You don’t want to be a person who slavishly adopts whatever opinion your teacher or some author gives you. On the other hand, you don’t want to reject all guidance from people who know what they are talking about. Autonomy is the median of knowing when to bow to authority and when not to, when to follow a role model and when not to, when to adhere to tradition and when not to.

Finally, there is generosity. This virtue starts with the willingness to share knowledge and give others credit. But it also means hearing others as they would like to be heard, looking for what each person has to teach and not looking to triumphantly pounce upon their errors.