The Metaphysical Club

The Metaphysical Club was a conversational philosophical club that the future Supreme Court Justice Oliver Wendell Holmes Jr., the philosopher and psychologist William James, and the philosopher Charles Sanders Peirce formed in January 1872 in Cambridge, Massachusetts, and dissolved in December 1872. Upon Peirce's arrival at Johns Hopkins University in 1879, he founded a new Metaphysical Club there. 
The name of the club was chosen "half-ironically, half-defiantly," according to Peirce, as the group rejected the radical foundationalist European metaphysics in favor of a moderate foundationalism, pursued critical thinking of a pragmatist and positivist nature. In fact, it was within these philosophical discussions that pragmatism is said to have been born.
Other members of the club included Chauncey Wright, John Fiske, Francis Ellingwood Abbot, Nicholas St. John Green, and Joseph Bangs Warner. The Metaphysical Club is never mentioned by any person within the club other than Peirce. The only other known person to have mentioned the club was Henry James, the great novelist and brother of William James.