At the Science of Consciousness conference last month in Tucson, I was faced with a quandary: Which of eight simultaneous sessions should I attend?

In one room, scientists and philosophers were discussing the physiology of brain cells and how they might generate the thinking mind. In another, the subject was free will — real or an illusion?

Next door was a session on panpsychism, the controversial (to say the least) idea that everything — animal, vegetable and mineral — is imbued at its subatomic roots with mindlike qualities. Running on parallel tracks were sessions titled “Phenomenal Consciousness,” the “Neural Correlates of Consciousness” and the “Extended Mind.”

For much of the 20th century, the science of consciousness was widely dismissed as an impenetrable mystery, a morass of a problem that could be safely pursued only by older professors as they thought deep thoughts in their endowed chairs. Beginning in the 1990s, the field slowly became more respectable.