"Neurons do not just fire and not fire . . . they must be capable of passing on much more subtle information than yes or no. They are not just hammers hitting the next nail, either more frequently or less so. They are, to complete this analogy, a carpenter’s kit, with screwdrivers, pliers, pincers, mallets—and hammers. . . . Each neural impulse is transformed along the way, and nowhere else than at the synapses."