David Eagleman in the New York Times:
Here’s why. Imagine you were an alien catching sight of the Earth. Your species knows nothing about humans, let alone how to interpret the interactions of seven billion people in complex social networks. With no acquaintance with the nuances of human language or behavior, it proves impossible to decipher the secret idiom of neighborhoods and governments, the interplay of local and global culture, or the intertwining economies of nations. It just looks like pandemonium, a meaningless Babel.
So it goes with the brain. We are the aliens in that landscape, and the brain is an even more complicated cipher. It is composed of 100 billion electrically active cells called neurons, each connected to many thousands of its neighbors. Each neuron relays information in the form of miniature voltage spikes, which are then converted into chemical signals that bridge the gap to other neurons. Most neurons send these signals many times per second; if each signaling event were to make a sound as loud as a pin dropping, the cacophony from a single human head would blow out all the windows. The complexity of such a system bankrupts our language; observing the brain with our current technologies, we mostly detect an enigmatic uproar.
More here.