From pg. 25 of Creativity: The Psychology of Discovery and Invention, a definition of creativity that illuminates what the book at large examines:
The problem is that in the term “creativity” as commonly used covers too much ground. It refers to very different entities, thus causing a great deal of confusion. To clarify the issues, I distinguish at least three different phenomena that can legitimately be called by that name.
The first usage, widespread in ordinary conversation, refers to persons who express unusual thoughts, who are interesting and stimulating–in short, to people who appear unusually bright. A brilliant conversationalist, a person with varied interests and a quick mind, may be called creative in this sense. Unless they also contribute something of permanent significance, I refer to people of this sort as brilliant rather than creative.
The second way the term can be used is to refer to people who experience the world in novel and original ways. These are individuals whose perceptions are fresh, whose judgments are insightful, who may make important discoveries that only they know about. I refer to such people as personally creative, and try to deal with them as much as possible. But given the subjective nature of this form or creativity, it is difficult to deal with no matter how important it is for those who experience it.
The final use of the term designates individuals who, like Leonardo, Edison, Picasso, or Einstein, have changed our culture in some important respect. They are the creative ones without qualifications. Because their achievements are by definition public, it is easier to write about them, and the persons included in my study belong to this group.
The difference among these three meanings is not just a matter of degree, The last kind of creativity is not simply a more developed form of the first two. These are actually different ways of being creative each to a large measure unrelated to the others. It happens very often, for example, that some persons brimming with brilliance, whom everyone thinks of as being exceptionally creative, never leave any accomplishment, any trace of their existence–except, perhaps, in the memories of those who have known them. Whereas some of the people who have had the greatest impact on history did not show any creativity or brilliance in their behavior, except for the accomplishments they left behind.
For example, Leonardo da Vinci, certainly one of the most creative persons in the third sense of the term, was apparently reclusive, and almost compulsive in his behavior. If you had met him at a cocktail party, you would have thought that he was a tiresome bore and would have left him standing in a corner as soon as possible. Neither Issac Newton nor Thomas Edison would have been considered assets at a party either, and outside of their scientific concerns they appeared colorless and driven. The biographers of outstanding creators struggle valiantly to make their subjects interesting and brilliant, yet more often than not their efforts are in vain, The accomplishments of a Michelangelo, a Beethoven, a Picasso, or an Einstein are awesome in their respective fields–but their private lives, their everyday ideas and actions, would seldom warrant another thought were it not that their specialized accomplishments made everything they said or did of interest.