Introduction: Toward an interdisciplinary science of spontaneous thought

Forthcoming chapter in The Oxford Handbook of Spontaneous Thought 2 Where do spontaneous thoughts come from? It may be surprising that the seemingly straightforward answers " from the mind " or " from the brain " are in fact an incredibly recent, modern understanding of the origins of spontaneous thought. For nearly all of human history, our thoughts – especially the most sudden, insightful, and important – were almost universally ascribed to divine or other external sources. Cultures around the world believed that dreams were messages sent from the gods (Kracke, 1991); inventions like writing and agriculture were credited to ancient culture heroes and tutelary deities long lost in the mists of legend (Chang, 1983); and the belief that artistic creativity was inspired by the Muses (Murray, 1989) held sway for two millennia (McMahon, 2013). Even the original sense of the word inspiration was that the divine had been 'breathed into' a mere mortal, accounting for the new idea or insight. There were of course exceptions – Aristotle, for instance, put forward the naturalistic hypothesis that dreams were created by the mind of the dreamer (Aristoteles & Gallop, 1996) – but nowhere, it seems, was there a widespread belief in the spontaneity, originality, and creativity of the unaided human mind. We still sometimes worship our great intellectual innovators – artists, scientists, philosophers – as semi-­‐divine figures. But somewhere, somehow, our perspective changed and we began to see ourselves as the authors of our own thoughts, however inexplicable their origins might seem. Perhaps the beginnings of this shift in perspective are echoed in the ancient myth of Prometheus, who " stole and gave to mortals " the " fount of the arts, the light of fire " – in other words, the power of conjuring up novel thoughts (Griffith, 1983). But although this internalization of thought's origins began long ago, only in the past few centuries have human beings truly taken responsibility for their own mental content, and Forthcoming chapter in The Oxford Handbook of Spontaneous Thought 3 finally localized thought to the central nervous system – laying the foundations for a protoscience of spontaneous thought. This shift has broadly answered the who and the where of spontaneous thought: we are the source of our thoughts, and these thoughts seem to be constructed in our heads. But enormous questions still loom: what, exactly, is spontaneous thought? Why does our brain engage …