May was influenced by American humanism, and interested in reconciling existential psychology with other philosophies, especially Freud's.
May considered Otto Rank (1884-1939) to be the most important precursor of existential therapy. Shortly before his death, May wrote the foreword to Robert Kramer's edited collection of Rank’s American lectures.
“I have long considered Otto Rank to be the great unacknowledged genius in Freud’s circle,”
wrote May (Rank, 1996, p. xi).May used some traditional existential terms in a slightly different fashion than others, and he invented new words for traditional existentialist concepts. Destiny, for example, could be "thrownness" combined with "fallenness"— the part of our lives that is determined for us, for the purpose of creating our lives. He also used the word "courage" to signify resisting anxiety.
He defined certain "stages" of development:
• Innocence – the pre-egoic, pre-self-conscious stage of the infant. An innocent is only doing what he or she must do. However, an innocent does have a degree of will in the sense of a drive to fulfill needs.
• Rebellion – the rebellious person wants freedom, but does not yet have a good understanding of the responsibility that goes with it.
• Decision – The person is in a transition stage in their life such that they need to be more independent from their parents and settle into the "ordinary stage". In this stage they must decide what to do with their life, and fulfilling rebellious needs from the rebellious stage.
• Ordinary – the normal adult ego learned responsibility, but finds it too demanding, and so seeks refuge in conformity and traditional values.
• Creative – the authentic adult, the existential stage, self-actualizing and transcending simple egocentrism.
These are not "stages" in the traditional sense. A child may certainly be innocent, ordinary or creative at times; an adult may be rebellious. The only association with certain ages is in terms of importance: rebelliousness is more important for a two year old or a teenager.
May perceived the sexual mores of the 1960s and 1970s, as well as commercialization of sex and pornography, as having influenced society such that people believed that love and sex are no longer associated directly. According to May, emotion has become separated from reason, making it acceptable socially to seek sexual relationships and avoid the natural drive to relate to another person and create new life. May believed that sexual freedom can cause modern society to neglect more important psychological developments. May suggests that the only way to remedy the cynical ideas that characterize our times is to rediscover the importance of caring for another, which May describes as the opposite of apathy.
His first book, The Meaning of Anxiety, was based on his doctoral dissertation, which in turn was based on his reading of the 19th century philosopher Søren Kierkegaard. His definition of anxiety is
He also quotes Kierkegaard:
"the apprehension cued off by a threat to some value which the individual holds essential to his existence as a self" (1967, p. 72).
In 1956, he edited the book Existence with Ernst Angel and Henri Ellenberger. Existence helped introduce existential psychology to the US.
"Anxiety is the dizziness of freedom".
“Love and Will” is another of May’s famous texts. This book investigates the shifting viewpoints of love and sex in human behaviour. During the “Sexual Revolution” in the 1960s, many individuals were exploring their sexuality. “Free sex” was replacing the ideology of free love. May explains that love is intentionally willed by an individual, whereas sexual desire is the complete opposite. Real human instinct reflected upon deliberation and consideration. May then shows that to give in to these impulses does not actually make one free, but to resist these impulses is the meaning of being free.