Platonic philosophy in the context of Set (mathematics)

Middle Platonism is the modern name given to a revival and outgrowth of Platonic philosophy, lasting from about 90 BC – when Antiochus of Ascalon rejected the scepticism of the new Academy – until the development of neoplatonism under Plotinus in the 3rd century. Middle Platonism absorbed many doctrines from the rival Peripatetic and Stoic schools. The pre-eminent philosopher in this period, Plutarch (c. 45–120), defended the freedom of the will and the immortality of the soul. He sought to show that God, in creating the world, had transformed matter, as the receptacle of evil, into the divine soul of the world, where it continued to operate as the source of all evil. God is a transcendent being, who operates through divine intermediaries, which are the gods and daemons of popular religion. Numenius of Apamea (c. 160) combined Platonism with neopythagoreanism and other eastern philosophies, in a move which would prefigure the development of neoplatonism.

Tyrannicide or tyrannomachia is the killing or assassination of a tyrant or unjust ruler, purportedly for the common good,and usually by one of the tyrant's subjects. Tyrannicide was legally permitted and encouraged in Classical Greece. Often, the term "tyrant" was a justification for political murders by rivals, but in some exceptional cases students of Platonic philosophy risked their lives against tyrants. The killing of Clearchus of Heraclea in 353 BC by a cohort led by his own court philosopher is an example of a tyrannicide. A person who carries out a tyrannicide is also called a "tyrannicide".

The term originally denoted the action of Harmodius and Aristogeiton, who are often called the Tyrannicides, in killing Hipparchus of Athens in 514 BC.

Michael Psellos or Psellus (Greek: Μιχαὴλ Ψελλός, romanized: Michaḗl Psellós, Byzantine Greek: [mixaˈil pseˈlːos]) was a Byzantine Greek monk, savant, writer, philosopher, imperial courtier, historian and music theorist. He was born in 1017 or 1018, and is believed to have died in 1078, although it has also been maintained that he remained alive until 1096. He served as a high ranking courtier and advisor to several Byzantine emperors and was instrumental in the re-positioning of power of those emperors. Psellos has made lasting contributions to Byzantine culture by advocating for the revival of Byzantine classical studies, which would later influence the Italian Renaissance, as well as by interpreting Homeric literature and Platonic philosophy as precursors and integral components of Christian doctrine. His texts combined theology, philosophy, and psychology. Among his most famous works are his Commentary on Plato's Teachings on the Origin of the Soul, and the Chronographia, a series of biographies from emperor Basil II to Nikephoros III, which serves as a valuable source on the history of the 11th century Byzantine Empire.