" Neuroscience tells us that it is highly improbable that we have souls, as everything we think and feel is no more or no less than the electrochemical chatter of our nerve cells. Our sense of self, our feelings and our thoughts, our love for others, our hopes and ambitions, our hates and fears all die when our brains die. Many people deeply resent this view of things, which not only deprives us of life after death but also seems to downgrade thought to mere electrochemistry and reduces us to mere automata, to machines. Such people are profoundly mistaken, since what it really does is upgrade matter into something infinitely mysterious that we do not understand. There are one hundred billion nerve cells in our brains. Does each one have a fragment of consciousness within it? How many nerve cells do we require to be conscious or to feel pain? Or does consciousness and thought reside in the electrochemical impulses that join these billions of cells together? Is a snail aware? Does it feel pain when you crush it underfoot? Nobody knows. "

― Henry Marsh , Do No Harm: Stories of Life, Death and Brain Surgery