Book excerpt: Corballis argues that mind-wandering has many constructive and adaptive features. These range from mental time travel?the wandering back and forth through time, not only to plan our futures based on past experience, but also to generate a continuous sense of who we are--to the ability to inhabit the minds of others, increasing empathy and social understanding. Through mind-wandering, we invent, tell stories, and expand our mental horizons. Mind wandering , hardly the sign of a faulty network or aimless distraction, actually underwrites creativity, whether as a Wordsworth wandering lonely as a cloud, or an Einstein imagining himself travelling on a beam of light. Corballis takes readers on a mental journey in chapters that can be savored piecemeal, as the minds of readers wander in different ways, and sometimes have limited attentional capacity.