Fillmore's distinctive contribution to New Thought theology is a method of reading scripture in which nothing in the text refers primarily to history. Every person, place and tribe in the Bible stands for something in the individual reader: a faculty, a state of consciousness, a habit of thought. The twelve disciples become twelve powers of the human being, faith, strength, judgement, love and the rest, each located and each capable of development. Egypt is bondage to materiality; Jerusalem is a state of peace within.
He set this out at length in the Metaphysical Bible Dictionary, which works through the proper names of the Old and New Testaments and assigns each one its inner meaning. The approach is not new in kind, since allegorical reading is as old as Philo and Origen, but the thoroughness is unusual, and it gave Unity a way of keeping Christian scripture at the centre while detaching almost every claim in it from historical assertion.
He read very widely outside Christianity, in Theosophy, in Hindu material, and in spiritualist literature, and some of his conclusions were eccentric even by the standards of his movement: he expected for a long period that the body could be regenerated indefinitely and death avoided. He was writing and lecturing into his nineties and died in 1948.