Larson's lifelong body of work reconstructs a complete version of the story of Christian origins and its theological controversies, detailing its evolution from the cults of Osiris and Dionysus to modern times. This includes the synthesis of ideas, deities and personalities that historically gave favor to Christianity against religious competitors such as Mithraism, which lacked a human founder and barred the general public, or Manichaeism, which lacked a deified founder. He summarizes the exposition of this story:
And so we see that Egypt gave the world the god-man savior, who was several times reconstituted in the Greek and barbarian mysteries. Persia filled the void with fears of hell, with hopes of paradise, and with the concept of the Last Judgment, and with the expectation of a renovated universe. The Jews and the Brahmanas gave us the priest-state. The Buddhists gave us renunciation, which made sex, family, wealth, labor and comfort into crimes and which made of idle communism and parasitism the saintly way of life. The Greeks gave us democracy and private property, which Pythagoras attempted to replace with a celibate but self-reliant communism. He also popularized the Zoroastrian metaphysics, the Brahmanic-Buddhist eschatology, and the Egyptian-Dionysiac soteriology in the Graeco-Roman world. Plato absorbed the communism, anthropology, and eschatology of Pythagoras, but rejected his celibacy and his soteriology, as well as his concept of religion as a mystery-cult. Aristotle rejected the features of Pythagoreanism which Plato accepted and embraced the concepts of private property and the secular life, in this respect returning to the ideology of Hesiod. The Essenes were Pythagoreans who encased their pagan religious synthesis, which Jesus absorbed, in a Jewish entegument, which he rejected, although He considered Himself one of the prophets of Yahweh; but he incorporated a definitely Buddhist element, not found among the Essenes. In the Gospel, therefore, we find a synthesis of Osirian-Dionysiac soteriology, Zoroastrian eschatology, Buddhist ethics and renunciation, Pythagorean communism, and the Essenic Parousia. (Origins 416-17)
Larson was also a tax critic and tax expert, who authored books on the immunities of organized religion, the Federal Reserve, and the IRS, including a text on The Theory of Logical Expression. His articles, including a series titled Our World in Conflict, have appeared in Parade Magazine, Fortune Magazine, Reader's Digest and other publications.