You might wonder, at some point today, what’s going on in another person’s mind. You may compliment someone’s great mind, or say they are out of their mind. You may even try to expand or free your own mind.

But what is a mind? Defining the concept is a surprisingly slippery task. The mind is the seat of consciousness, the essence of your being. Without a mind, you cannot be considered meaningfully alive. So what exactly, and where precisely, is it?

Traditionally, scientists have tried to define the mind as the product of brain activity: The brain is the physical substance, and the mind is the conscious product of those firing neurons, according to the classic argument. But growing evidence shows that the mind goes far beyond the physical workings of your brain.