Spiritism is, at the same time, a science of observation and a philosophical doctrine. As a practical science, it consists of the relationships established between us and the spirits; as a philosophy, it encompasses all the moral consequences that stem from these same relationships. We can define it as follows: Spiritism is a science that deals with the nature, origin, and destiny of spirits, as well as their relationships with the physical world. (Allan Kardec, What is Spiritism, p. 40).
Spiritism does not have the isolated character of a philosophy or a religion because it is simultaneously religion, philosophy, and science. It is both divine revelation and the work of cooperation between disembodied and embodied human spirits. It has the singular characteristic of being impersonal, complementary, and progressive; first, because it is not the product of the revelation of a single spirit or the work of a single man, second, because it is the natural, explicit, and logical complement of the two previous divine revelations (that of Moses and that of Christ), third, because, as Kardec said, it will never have the final word.
IT IS SCIENCE – Because it investigates, experiments, proves, systematizes concepts, laws, facts, forces, and phenomena of life, nature, thought, and human feelings.
IT IS PHILOSOPHY – Because it considers, induces, and deduces logical ideas and facts about the first cause and its natural effects, generalizes, and synthesizes, reflects, deepens, and explains, studies, discerns, defines motives and consequences.
IT IS RELIGION – Because from its scientific findings and philosophical conclusions, comes the knowledge of Divine parenthood and the universal brotherhood of all beings of Creation, establishing thus the natural worship of the love of God and of one's neighbor.
Infinitely superior to all limited sciences, it dispenses with sophisticated laboratories, expensive equipment, and rigid empirical methods. Infinitely more effective than all other known philosophies, it does not get lost in intellectual fantasies, nor is it limited exclusively to materially verifiable phenomena or deducible through insufficient reasoning of mathematical logic. Incomparably more rational and efficient than any other religion, it dispenses with priesthood, altars, rituals, and dogmas because it acts directly on the understanding and heart of each person, speaks to the soul of each individual, and establishes its empire in the mind of every being. (Áureo, Universe and Life, 4th ed., p.163-166, psych. Hernani T. Santanna).