John Searle has written that "the dirty secret of contemporary neuroscience is that so far we do not have a unifying theoretical
principle of neuroscience" in the way that we have an atomic theory of matter, a germ theory of disease, or a blood-pumping theory of the heart. The basic theories of how impulses are conducted along nerve fibres by electrical activity, and transmitted from one neuron to the next by chemical transmitters, can account for simple phenomena like reflex activity, how touching a hot stove makes one immediately withdraw one's hand. What we
don't understand is how nerve impulses going round and round in Beethoven's brain resulted in him composing the 9th Symphony.