FOR new ideas new words are needed, in order to secure clearness of language by avoiding the confusion inseparable from the employment of the same term for expressing different meanings. The words spiritual, spiritualist, spiritualism, have a definite acceptation; to give them a new one, in order to apply them to the doctrine set forth by spirits, would be to multiply the causes of amphibology, already so numerous. Strictly speaking, Spiritualism is the opposite of Materialism; every one is a Spiritualist who believes that there is in him something more than matter, but it does not follow that he believes in the existence of spirits, or in their communication with the visible world. Instead, therefore, of the words SPIRITUAL SPIRITUALISM, we employ, to designate this latter belief, the words SPIRITIST, SPIRITISM, which, by their form, indicate their origin and radical meaning, and have thus the advantage of being perfectly intelligible; and we reserve the words spiritualism, spiritualist, for the expression of the meaning attached to them by common acceptation. We say, then, that the fundamental principle of the spiritist theory, or Spiritism, is the relation of the material world with spirits, or the beings of the invisible world; and we designate the adherents of the spiritist theory as spiritists. In a special sense, "THE SPIRITS' BOOK" contains the doctrine or theory of spiritism; in a general sense, it appertains to the spiritualist school, of which it presents one of the phases. It is for this reason that we have inscribed the words Spiritualist Philosophy on its title-page. Allan Kardec is the pen name of the French teacher and educator Hippolyte Leon Denizard known as the systematizer of Spiritism for which he laid the foundation with the five books of the Spiritist Codification.