History of Jehovah's Witnesses book, "Three Worlds and the Harvest of This World", was published in early 1877. It articulated ideas that remained the teachings of Russell's associates for the next 40 years, many of which are still embraced by Jehovah's Witnesses: it identified a 2520-year-long era called "the Gentile Times", which would end in 1914, and broke from Adventist teachings by advancing Russell's concept of "restitution" — that all humankind since Adam would be resurrected to the earth and given the opportunity for eternal perfect human life. Russell claimed it was the first book to combine biblical end-time prophecies with the concept of
Development of Jehovah's Witnesses doctrine through his holy spirit. A 1930 publication claimed God used "invisible deputies" and "invisible angels" to pass his "messages" to "The Watchtower", although "The Watchtower" told Witnesses it was not necessary for them to understand how this took place. A 1973 policy change to disfellowship tobacco users was explained as a decision that "Jehovah has brought to the attention of his 'holy' people". Watch Tower publications often cite Proverbs 4:18, "The path of the righteous ones is like the bright light that is getting lighter and lighter until the day is firmly established" ("NWT") when explaining the need to change