In the fields I know best, among the life sciences, it is required that the most expert and sophisticated minds be capable of changing course - often with a great lurch - every few years.

As evolutionary time is measured, we have only just turned up and have hardly had time to catch breath, still marveling at our thumbs, still learning to use the brand-new gift of language. Being so young, we can be excused all sorts of folly and can permit ourselves the hope that someday, as a species, we will begin to grow up.

Music is the effort we make to explain to ourselves how our brains work. We listen to Bach transfixed because this is listening to a human mind.

Selfness is an essential fact of life. The thought of nonselfness, precise sameness is terrifying.

The earliest sensation at the onset of illness, often preceding the recognition of identifiable symptoms, is apprehension. Something has gone wrong, and a glimpse of mortality shifts somewhere deep in the mind. It is the most ancient of our fears.

If we had better hearing, and could discern the descants of sea birds, the rhythmic tympani of schools of mollusks, or even the distant harmonics of midges hanging over meadows in the sun, the combined sound might lift us off our feet.

It is my belief, based partly on personal experience but partly also arrived at by looking around at others, that childhood lasts considerably longer in the males of our species than in the females.