An encyclopedia (also spelled encyclopaedia or encyclopædia) is a type of reference work, a compendium holding a summary of information from either all branches of knowledge or a particular branch of knowledge. Encyclopedias are divided into articles or entries, which are usually accessed alphabetically by article name. Encyclopedia entries are longer and more detailed than those in most dictionaries. Generally speaking, unlike dictionary entries, which focus on linguistic information about words, encyclopedia articles focus on factual information to cover the thing or concept for which the article name stands.

Encyclopedias have existed for around 2,000 years; the oldest still in existence, Naturalis Historia, was written in ca. 77 AD by Pliny the Elder. The modern encyclopedia evolved out of dictionaries around the 17th century. Historically, some encyclopedias were contained in one volume, but some, such as the Encyclopædia Britannica or the world´s largest Enciclopedia universal ilustrada europeo-americana, became huge multi-volume works. Some modern encyclopedias, such as Wikipedia, are electronic and are often freely available.

Lev Nikolayevich Tolstoy (Russian: Лев Никола́евич Толсто́й, pronounced [lʲev nʲɪkɐˈlaɪvʲɪtɕ tɐlˈstoj] ( listen); known in the Anglosphere as Leo Tolstoy) (September 9, 1828 – November 20, 1910) was a Russian writer who primarily wrote novels and short stories. Later in life, he also wrote plays and essays. His two most famous works, the novels War and Peace and Anna Karenina, are acknowledged as two of the greatest novels of all time and a pinnacle of realist fiction. Many consider Tolstoy to have been one of the world's greatest novelists. Tolstoy is equally known for his complicated and paradoxical persona and for his extreme moralistic and ascetic views, which he adopted after a moral crisis and spiritual awakening in the 1870s, after which he also became noted as a moral thinker and social reformer.

His literal interpretation of the ethical teachings of Jesus, centering on the Sermon on the Mount, caused him in later life to become a fervent Christian anarchist and anarcho-pacifist. His ideas on nonviolent resistance, expressed in such works as The Kingdom of God Is Within You, were to have a profound impact on such pivotal twentieth-century figures as Mohandas Gandhi and Martin Luther King, Jr.

William James (January 11, 1842 – August 26, 1910) was a pioneering American psychologist and philosopher who was trained as a physician. He was the first educator to offer a psychology course in the U.S. He wrote influential books on the young science of psychology, educational psychology, psychology of religious experience and mysticism, and on the philosophy of pragmatism. He was the brother of novelist Henry James and of diarist Alice James. In the summer of 1878, James married Alice Gibbens.

William James was born at the Astor House in New York City. He was the son of Henry James Sr., a noted and independently wealthy Swedenborgian theologian well acquainted with the literary and intellectual elites of his day. The intellectual brilliance of the James family milieu and the remarkable epistolary talents of several of its members have made them a subject of continuing interest to historians, biographers, and critics.

James interacted with a wide array of writers and scholars throughout his life, including his godfather Ralph Waldo Emerson, his godson William James Sidis, as well as Charles Sanders Peirce, Bertrand Russell, Josiah Royce, Ernst Mach, John Dewey, Macedonio Fernández, Walter Lippmann, Mark Twain, Horatio Alger, Jr., Henri Bergson and Sigmund Freud.