Such evidence is not the only kind which produces belief; though positivism maintains that it is the only kind which ought to produce so high a degree of confidence as all minds have or can be made to have through their agreements.

In 1872 Wright helped found The Metaphysical Club with other Harvard intellectuals such as Charles Sanders Peirce William James and Oliver Wendell Holmes Jr. Although in general he adhered to the evolution theory he was a free-lancer in thought. In 1852 he graduated at Harvard and became computer to the American Ephemeris and Nautical Almanac.