Sam Treiman... has quoted something he called Treiman's theorem... Impossible things usually don't happen.... With the discovery of radioactivity... it suddenly became apparent that the "impossible" was happening all the time. Uranium, thorium, radium... fit all the requirements of chemical elements. They could not be broken down by any of the standard methods... But occasionally... atoms of these elements spontaneously changed into other kinds of atoms.... So what is left of the doctrine of the elements? Is alchemy reinstated? Not at all. The point is that the doctrine fails only under rare or special conditions.... We can isolate the conditions in which they do, and retain a more restricted but still useful concept of the "impossible."

Longing for the Harmonies: Themes and Variations from Modern Physics (1987)