“ A human body is one persisting thing for common sense, but for physics its matter is constantly changing. ”
 Bertrand Russell, Mysticism and Logic and Other Essays (1910). copy citation

Context

“in different biographies as appearances of the same momentary state of a thing, we shall have all that is necessary for the complete construction of the history of a thing. It is to be observed, to begin with, that the identity of a thing for common sense is not always correlated with the identity of matter for physics. A human body is one persisting thing for common sense, but for physics its matter is constantly changing. We may say, broadly, that the common-sense conception is based upon continuity in appearances at the ordinary distances of sense-data, while the physical conception is based upon the continuity of appearances at very small distances from the thing.” source