In the 1850s, the Société became interested in Spiritualism, believing that some people—while in a mesmeric trance—could become clairvoyant and communicate with the dead. In 1857, Barthet founded Le Spiritualiste, the country’s only French-language publication on Spiritualism, which he used as a platform to explain Spiritualist philosophies and report on séances and mediums throughout the country. In its monthly issues, Le Spiritualiste also provided a detailed look at the Spiritualist movement in New Orleans, providing schedules and recaps of local public séances and listing events that featured local speakers and mediums.

Spiritualism in New Orleans found popularity among a wide swath of people—French and American, Black and white. One local practitioner mentioned in the listings is a Mr. Valmour (d. 1869), a blacksmith and free man of color who provided both public séances and healing services. Valmour became a spiritual mentor to another free man of color, Henry Louis Rey (1831–1894). In 1858, Rey founded the Cercle Harmonique, a small group of Afro-Creole men who received messages from the spirits that encouraged equality and harmony among people, making the group an early leader in the pursuit of civil rights in the city. According to these messages, it was up to members of the Cercle to make the world a better place by counteracting greed and corruption.

Le Spiritualiste was constantly criticized by Abbé Napoleon-Joseph Perché (1805–1883), future archbishop of New Orleans and known white supremacist, in the local diocese publication Le Propagateur Catholique. Additionally, many of the séances announced in Le Spiritualiste were raided by police. When Barthet ceased publishing after just two years, he cited a decline in readership, but these other conflicts may have contributed to Le Spiritualiste’s end as well.