What do we mean by "knowledge" or "understanding"? And how do billions of neurons achieve them? These are complete mysteries. Admittedly, cognitive neuroscientists are still very vague about the exact meaning of words like "understand," "think," and indeed the word "meaning" itself.

People often ask how I got interested in the brain; my rhetorical answer is: 'How can anyone NOT be interested in it?' Everything you call 'human nature' and consciousness arises from it.

There are 100 billion neurons in the adult human brain, and each neuron makes something like 1,000 to 10,000 contacts with other neurons in the brain. Based on this, people have calculated that the number of permutations and combinations of brain activity exceeds the number of elementary particles in the universe.

Self-awareness is a trait that not only makes us human but also paradoxically makes us want to be more than merely human. As I said in my BBC Reith Lectures, “Science tells us we are merely beasts, but we don’t feel like that. We feel like angels trapped inside the bodies of beasts, forever craving transcendence

Even today no computer can understand language as well as a three-year-old or see as well as a mouse.

The adage that fact is stranger than fiction seems to be especially true for the workings of the brain.

Here is this three-pound mass of jelly you can hold in the palm of your hand, and it can contemplate the vastness of interstellar space. It can contemplate the meaning of infinity and it can contemplate itself contemplating on the meaning of infinity.