New words are needed to convey new ideas clearly and to avoid the inevitable confusion that ensues from using the same term for expressing different concepts. The words spiritual, spiritualist, and spiritualism each have a given meaning that is specifc. To attribute a new meaning to these words by applying it to Spiritism merely increases the numerous causes of ambiguity that already exist.
In actuality, spiritualism is the opposite of materialism. Anyone who believes that something more than matter exists inside of us is a spiritualist, but this does not necessarily mean that they believe in the existence of spirits or their communication with the physical world. It is with this distinction in mind that we avoid the use of spiritual and spiritualism and instead, use Spiritist and Spiritism to describe the latter belief. These words indicate their origin and root meaning, and have the advantage of being perfectly clear and understandable. Therefore, we reserve the word spiritualism for its commonly accepted meaning and the central principle of Spiritism as the relationship of the physical world with spirits or beings that inhabit the invisible world. We refer to the adherents and supporters of Spiritism as Spiritists.
The Spirits’ Book contains the principles of Spiritism, which is generally associated with the spiritualist school, of which it presents one perspective. This is why Spiritualist Philosophy appears at the top of the title page.