Why are we obsessed with the things we want only to be bored when we get them?  Why is addiction perfectly logical to an addict?  Why does love change so quickly from passion to indifference?  Why are some people die-hard liberals and others hardcore conservatives?  Why are we always hopeful for solutions even in the darkest times—and so good at figuring them out?  The answer is found in a single chemical in your brain: dopamine. Dopamine ensured the survival of early man. Thousands of years later, it is the source of our most basic behaviors and cultural ideas—and progress itself.  Dopamine is the chemical of desire that always asks for more—more stuff, more stimulation, and more surprises. In pursuit of these things, it is undeterred by emotion, fear, or morality. Dopamine is the source of our every urge, that little bit of biology that makes an ambitious business...