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Self- knowledge is an ancient question, fea -
turing prominently in ancient Greek cul -
ture and philosophy. The Oracle at Delphi 
famously proclaimed, “Know thyself,” 
and Socrates was known for emphasizing 
his awareness of his own ignorance. Self- 
knowledge is also the topic of many self-help 
books, and the goal of many clients seek -
ing therapy. Even when psychotherapy cli -
ents do not seek self-  knowledge, therapists 
commonly evaluate clients’ mental health 
based on their insight1 into their own per -
sonality or dysfunction. But philosophers 
and therapists are not the only ones who 
care (or should care) about self-  knowledge. 
Lack of self-  insight underlies many of the 
obstacles we face in daily life. It is an indi -
vidual problem that leads to poor decisions, 
an interpersonal problem that affects close 
relationships and organizations, and a soci -
etal problem with implications for economic 
and social policy (Anderson, Ames, & Gos -
ling, 2008; Brett & Atwater, 2001; Carlson, 
2016a, 2016b; Dunning, Heath, & Suls, 
2004). Thus, understanding the strengths 
and limits of self-  insight could shed light 
on both the challenges people face in their 
personal lives and those faced by couples, 
groups, and nations.Why should personality psychologists, in 
particular, care about self-  knowledge? First, 
people are likely to vary in self-  knowledge, 
and these individual differences may be re -
lated in interesting ways to other important 
constructs (e.g., intelligence, interpersonal 
accuracy, narcissism, wisdom). For example, 
self- knowledge likely requires the ability to 
notice one’s own behavior and others’ reac -
tions in distracting social situations, and as 
such, might be related to higher cognitive 
functioning abilities such as working mem -
ory. Second, testing whether people have 
self- knowledge of their personalities informs 
theories about traits and the self. With re -
spect to traits, learning which traits are (not) 
accessible to the self can help us understand 
how traits differ from each other. With re -
spect to theories about the self, identify -
ing the blind spots in self-  knowledge might 
shed light on the cognitive and motivational 
processes that shape the self. Third, the ac -
curacy of self-  reports of personality has 
vast methodological implications for both 
personality research and applied fields that 
rely on personality measures. In particular, 
learning when self-  reports are suspect will 
help us develop better assessment methods.
Much of our interest in self-  knowledge CHAPTER 41
What Do We Know  
When We Know Ourselves?
Simine  Vazire  
Erika  N. Carlson