I certainly don't pretend in this short book to have made sense of everything, but I have tried to
identify some connections among plausible answers to the most serious philosophical problems.
Questions about how to pursue knowledge and how to pursue morality require answers that are both
descriptive and normative. We want to know both how we do form beliefs and how we ought to form
beliefs, just as we want to know both how people behave and how they ought to behave. In both
epistemology and ethics, however, the descriptive and normative questions can be tied together by
considerations of past experience and coherence of different kinds of practice with different kinds of
goals, such as the most fundamental needs and interests. Such links between descriptive and
normative conclusions fit well with the naturalistic view of reality that minds are a complex, brainbased
part of an entirely physical universe.
The same combination of empirical, theoretical, and normative considerations has served to
generate answers to the question of why life is worth living. Goals concerning love, work, and play
are connected to vital needs of human beings that can be identified through empirical investigation.
This research is often part of the social sciences, using empirical techniques established in
psychology, economics, and sociology. But insights are increasingly streaming from the investigation
of the biological mechanisms operating in human brains. We know more and more about how
activities are marked as rewarding through interactions of brain areas involved in cognition and
emotion, such as the prefrontal cortex, the amygdala, and the nucleus accumbens. These investigations
enable us not only to use the social sciences to identify that love, work, and play matter to people, but
also to use neuroscience to learn how they matter to people through brain functioning. We thus get an
understanding of how the goals related to these realms of life are tied to the deep objective interests
of human beings.