Plotinus was a Hellenistic Platonist philosopher, born and raised in Roman Egypt. Plotinus is regarded by modern scholarship as the founder of Neoplatonism. His teacher was the self-taught philosopher Ammonius Saccas, who belonged to the Platonic tradition. Historians of the 19th century invented the term "neoplatonism" and applied it to refer to Plotinus and his philosophy, which was vastly influential during late antiquity, the Middle Ages, and the Renaissance. Much of the biographical information about Plotinus comes from Porphyry's preface to his edition of Plotinus' most notable literary work, The Enneads. In his metaphysical writings, Plotinus described three fundamental principles: the One, the Intellect, and the Soul. His works have inspired centuries of Pagan, Jewish, Christian, Gnostic, and early Islamic metaphysicians and mystics, including developing precepts that influence mainstream theological concepts within religions, such as his work on duality of the One in two metaphysical states.

Plutarch was a Greek Middle Platonist philosopher, historian, biographer, essayist, and priest at the Temple of Apollo in Delphi. He is known primarily for his Parallel Lives, a series of biographies of illustrious Greeks and Romans, and Moralia, a collection of essays and speeches. Upon becoming a Roman citizen, he was possibly named Lucius Mestrius Plutarchus.

Polybius was a Greek historian of the middle Hellenistic period. He is noted for his work The Histories, a universal history documenting the rise of Rome in the Mediterranean in the third and second centuries BC. It covered the period of 264–146 BC, recording in detail events in Italy, Iberia, Greece, Macedonia, Syria, Egypt and Africa, and documented the Punic Wars and Macedonian Wars among many others.

Porter Emerson Browne was an American playwright, born Beverly, Massachusetts.

Poul William Anderson was an American fantasy and science fiction author who was active from the 1940s until the 21st century. Anderson also wrote historical novels. His awards include seven Hugo Awards and three Nebula Awards.

Prentice Mulford was an American literary humorist and California author. In addition, he was pivotal in the development of the thought within the New Thought movement. Many of the principles that would become standard in the movement, including the Law of Attraction, were clearly laid out in his Your Forces and How to Use Them, released as a series of essays during 1886–1892.

Colonel Prentiss Ingraham was a colonel in the Confederate Army, a mercenary throughout the 1860s, and a fiction writer.

Preserved Smith was an American historian of the Protestant Reformation.

Proclus Lycius, called Proclus the Successor, was a Greek Neoplatonist philosopher, one of the last major classical philosophers of late antiquity. He set forth one of the most elaborate and fully developed systems of Neoplatonism and, through later interpreters and translators, exerted an influence on Byzantine philosophy, Early Islamic philosophy, and Scholastic philosophy.

Procopius of Caesarea was a prominent late antique Roman (Byzantine) scholar and historian from Caesarea Maritima. Accompanying the Roman general Belisarius in Emperor Justinian's wars, Procopius became the principal Roman historian of the 6th century, writing the History of the Wars, the Buildings, and the Secret History.