James studied closely the schools of thought known as associationism and spiritualism. The view of an associationist is that each experience that one has leads to another, creating a chain of events. The association does not tie together two ideas, but rather physical objects. This association occurs on an atomic level. Small physical changes occur in the brain which eventually form complex ideas or associations. Thoughts are formed as these complex ideas work together and lead to new experiences. Isaac Newton and David Hartley both were precursors to this school of thought, proposing such ideas as "physical vibrations in the brain, spinal cord, and nerves are the basis of all sensations, all ideas, and all motions..." James disagreed with associationism in that he believed it to be too simple. He referred to associationism as "psychology without a soul" because there is nothing from within creating ideas; they just arise by associating objects with one another.
On the other hand, a spiritualist believes that mental events are attributed to the soul. Whereas in associationism, ideas and behaviors are separate, in spiritualism, they are connected. Spiritualism encompasses the term innatism, which suggests that ideas cause behavior. Ideas of past behavior influence the way a person will act in the future; these ideas are all tied together by the soul. Therefore, an inner soul causes one to have a thought, which leads them to perform a behavior, and memory of past behaviors determine how one will act in the future.
James had a strong opinion about these schools of thought. He was, by nature, a pragmatist and thus took the view that one should use whatever parts of theories make the most sense and can be proven. Therefore, he recommended breaking apart spiritualism and associationism and using the parts of them that make the most sense. James believed that each person has a soul, which exists in a spiritual universe, and leads a person to perform the behaviors they do in the physical world. James was influenced by Emanuel Swedenborg, who first introduced him to this idea. James stated that, although it does appear that humans use associations to move from one event to the next, this cannot be done without this soul tying everything together. For, after an association has been made, it is the person who decides which part of it to focus on, and therefore determines in which direction following associations will lead. Associationism is too simple in that it does not account for decision-making of future behaviors, and memory of what worked well and what did not. Spiritualism, however, does not demonstrate actual physical representations for how associations occur. James combined the views of spiritualism and associationism to create his own way of thinking.
James was a founding member and vice president of the American Society for Psychical Research. The lending of his name made Leonora Piper a famous medium. In 1885, the year after the death of his young son, James had his first sitting with Piper at the suggestion of his mother-in-law. James was soon convinced that Piper knew things she could only have discovered by supernatural means. He expressed his belief in Piper by saying, "If you wish to upset the law that all crows are black, it is enough if you prove that one crow is white. My white crow is Mrs. Piper." However, James did not believe that Piper was in contact with spirits. After evaluating sixty-nine reports of Piper's mediumship he considered the hypothesis of telepathy as well as Piper obtaining information about her sitters by natural means such as her memory recalling information. According to James the "spirit-control" hypothesis of her mediumship was incoherent, irrelevant and in cases demonstrably false.
James held séances with Piper and was impressed by some of the details he was given, however, according to Massimo Polidoro a maid in the household of James was friendly with a maid in Piper's house and this may of been a source of information that Piper used for private details about James. Bibliographers Frederick Burkhardt and Fredson Bowers who compiled the works of James wrote "It is thus possible that Mrs. Piper's knowledge of the James family was acquired from the gossip of servants and that the whole mystery rests on the failure of the people upstairs to realize that servants [downstairs] also have ears."