As discussed in Irish Philosophy, de Selby believed human existence was "a succession of static experiences each infinitely brief" and "a journey is a hallucination" which he demonstrated by travelling from Bath to Folkestone by means of picture postcards of the supposed route, barometric instruments, clocks and a device to regulate gaslight to simulate sunlight at various "times" of day. Another theory of de Selby's was that mirrors held the secret to eternity, claiming a huge array of parallel mirrors allowed him to see his own face as a boy of twelve.