Harriet Emilie Cady was an American homeopathic physician and author of New Thought spiritual writings. Her 1896 book Lessons in Truth: A Course of Twelve Lessons in Practical Christianity is now considered one of the core texts on Unity Church teachings. It has sold over 1.6 million copies since its first publication.

The New Thought movement is a new religious movement that coalesced in the United States in the early 19th century. New Thought was seen by its adherents as succeeding "ancient thought", accumulated wisdom and philosophy from a variety of origins, such as Ancient Greek, Roman, Egyptian, Chinese, Taoist, Hindu, and Buddhist cultures and their related belief systems, primarily regarding the interaction among thought, belief, consciousness in the human mind, and the effects of these within and beyond the human mind. Though no direct line of transmission is traceable, many adherents to New Thought in the 19th and 20th centuries claimed to be direct descendants of those systems.