Phi Sigma Tau was founded at Muhlenberg College in 1930 as Alpha Kappa Alpha, with chapters at colleges in
Maryland and Pennsylvania. It remained in this regional status until October of 1955, when it was incorporated as
Phi Sigma Tau, a National Honor Society in Philosophy. Its essential purpose was and is to promote ties among philosophy departments in accredited institutions and students in philosophy nationally. Both on the local and national
levels, Phi Sigma Tau considers its organization as instrumental: a means for developing and honoring academic excellence as well as philosophical interest. In addition to providing a means of awarding distinction to students having
high scholarship and interest in philosophy, the Society also promotes interest in philosophy among the general collegiate public. Under Internal Revenue Service regulations, Phi Sigma Tau is a 501(c)(3) nonprofit corporation.
In 1955, Phi Sigma Tau included twelve chapters in Ohio, Tennessee, Maryland, Washington, D.C., New Mexico,
California, and Louisiana. By 1958 ten additional chapters had been added, including those which had formerly constituted Alpha Kappa Alpha; and the date of the latter's founding was taken as Phi Sigma Tau's founding date. In
1958 the Society was admitted to full membership in the Association of College Honor Societies (ACHS), and by
1969 its chapter network included 55 chapters in 32 states. The Society became international in 1991 with the installation of its first Canadian chapter; and, as of August, 2018, its chapter network includes over 200 chapters.