Much of what is colloquially meant by personality is the result of either intelligence or mental idiosyncrasies that, in their extreme form, become mental illness. Thus, it would seem that, in the preceding chapters on intelligence and mental illness, we have already discussed some aspects of personality. It is then a fair question to ask, what do psychologists or psychiatrists mean when they speak of personality?
Certainly, the general emotional state of a person is an important component of personality, but this is very hard to measure objectively. The state of relations between one person and the others around him are also critically important, and also hard to quantify. The factors that motivate an individual are central to their personality, but even people with a great deal of self-knowledge may be puzzled by some of their own actions, and it is not uncommon for people to have a poor grasp of their own underlying motives. Similarly, interests and aptitudes can define a person, but so many people share interests and aptitudes that this would seem an imprecise way of distinguishing between people. Finally, attitudes hold a central place in one's personality, but attitudes are often deeply held and highly emotional without having a strong rational basis. Consequently, people often have a difficult time reflecting on or discussing their own attitudes. And even a trained psychologist or psychiatrist may need lengthy sessions with a patient before the deeper motivations of that person can be understood.