[5][6] The family immigrated to the United States from Germany when Felix was six years old so that his father could accept the appointment as head rabbi at Temple Emanu-El in New York.

[9] While in Germany, he was strongly influenced by neo-Kantianism, especially the notions that one cannot prove or disprove the existence of a deity or immortality, and that morality can be established independently of theology.

When Adler returned to New York at the age of twenty-three, he was asked to give a sermon at Temple Emanu-El, where he was meant to follow in his father's footsteps as rabbi of the congregation.

[7] In 1874, after it had become clear that he would not become a rabbi, members of his father's congregation helped Adler gain a teaching position at Cornell University as a nonresident Professor of Hebrew and Oriental literature.

[10] In 1876, Adler, at age 26, was invited to give a lecture expanding upon his themes first presented in the sermon at Temple Emanu-El.

In February 1877, aided by Joseph Seligman, president of Temple Emanu-El, Adler incorporated the Society of Ethical Culture.

Because it served the working poor, the kindergarten provided basic necessities for the children when needed, such as clothing and hot meals.

Throughout his life, he always looked beyond the immediate concerns of family, labor, and race to the long-term challenge of reconstructing institutions, such as schools and government, to promote greater justice in human relations.

By the late 1890s, with the increase in international conflicts, Adler switched his concern from domestic issues to the question of American foreign policy.

While some contemporaries viewed the 1898 Spanish–American War as an act to liberate the Cubans from Spanish rule, others perceived the U.S. victories in the Caribbean and the Philippines as the beginning of an expansionist empire.

Ethical Culture affirms "the supreme worth of the person", and Adler superimposed this tenet on international relations, believing that no single group could lay claim to superior institutions and lifestyle.

Combining a supreme moral principle similar to Kant's with his detailed ideas of self-realization, he emphasized the free development of the individual about societal concerns and fellowship.

He characterized a virtuous act as one "in which the ends of self and of the other are respected and promoted jointly," coordinating Kantian universalistic imperative ethics with a type of perfectionism.

He felt consequentialism, particularly utilitarianism, was inappropriate in ethics as it attempts to apply quantitative measures to something of a qualitative nature.

Ethical Culture societies were formed in the late nineteenth century in numerous cities in the United States, for instance, Philadelphia and St. Louis.