An expert on petroleum geology and mineralogy, Mather was a prominent scholar, advocate for academic freedom, social activist, and critic of McCarthyism.

He is known for his efforts to harmonize the dialogue between science and religion, his role in the Scopes "Monkey Trial", his faith-based liberal activism, support for adult education programs and advocacy for civil liberties.

For the trial he submitted a deposition for the defense and helped Clarence Darrow rehearse his questioning of William Jennings Bryan.

Offended by methods and claims of the anti-evolutionists, he declared that his love of religion, as well as his commitment to science, drove him to oppose William Jennings Bryan and the prosecutors of organic evolution.

From the academy, to the court room and on the national stage, Mather was a determined advocate and activist for academic freedom and human rights.

A harbinger of Mather's willingness to stakeout unpopular positions in the service of academic freedom is what his biographer, Kennard Bork refers to as the “Kornhauser Affair” at Denison University in 1922.

In this instance Mather championed the cause of Professor Sidney I. Kornhauser[8] whose failure to achieve tenure was perceived by many colleagues to involve anti-semitic or anti-liberal bias among some university supporters and members of the administration.

[11] The loyalty oath was adopted by the Massachusetts state legislature and enforced by Harvard President James B. Conant.

[14] A measure of the Red Scare price that Mather would pay for his activism is reflected in the April 4, 1949, issue of Life magazine.

In an article subsection titled Dupes and Fellow Travelers Dress Up Communist Fronts, Mather is pictured among 50 prominent academics, scientists, clergy and writers, including Albert Einstein, Arthur Miller, Lillian Hellman, Langston Hughes, Norman Mailer and fellow Harvard professors, F.O.

Upon his retirement from Harvard in 1954, he and Marie traveled widely around the world, finally settling in Albuquerque, New Mexico, where he resided until his death at the age of 90.

In addition to the legacy of his scholarship, he stands among prominent twentieth century American scientists who sought to harmonize the dialogue between science and religion and to ally himself with progressive social causes.

[17]Kirtley Mather's remarkable career long efforts in the fields of science, religion, education and civil liberties brought him recognition, criticism and honor.