In logic and philosophy
The symbolic meanings of the number four are linked to those of the cross and the square. "Almost from prehistoric times, the number four was employed to signify what was solid, what could be touched and felt. Its relationship to the cross (four points) made it an outstanding symbol of wholeness and universality, a symbol which drew all to itself". Where lines of latitude and longitude intersect, they divide the earth into four proportions. Throughout the world kings and chieftains have been called "lord of the four suns" or "lord of the four quarters of the earth", which is understood to refer to the extent of their powers both territorially and in terms of total control of their subjects doings. The Square of Opposition, in both its Aristotelian version and its Boolean version, consists of four forms: A ("All S is R"), I ("Some S is R"), E ("No S is R"), and O ("Some S is not R"). In regard to whether two given propositions can have the same truth value, there are four separate logical possibilities: the propositions are subalterns (possibly both are true, and possibly both are false); subcontraries (both may be true, but not that both are false); contraries (both may be false, but not that both are true); or contradictories (it is not possible that both are true, and it is not possible that both are false). Aristotle held that there are basically four causes in nature: the material, the formal, the efficient, and the final.
Four Evangelists – Matthew, Mark, Luke, and John
Four Doctors of Western Church – Saint Gregory the Great, Saint Ambrose, Saint Augustine, and Saint Jerome
Four Doctors of Eastern Church – Saint John Chrysostom, Saint Basil the Great, and Gregory of Nazianzus and Saint Athanasius
Four Galilean moons of Jupiter – Io, Europa, Ganymede, and Callisto
The Gang of Four was a Chinese communist political faction. The Fantastic Four: Mr. Fantastic, The Invisible Woman, The Human Torch, The Thing. The Teenage Mutant Ninja Turtles: Leonardo, Michelangelo, Donatello, Raphael
The Beatles were also known as the "Fab Four": John Lennon, Paul McCartney, George Harrison, Ringo Starr. Gang of Four is a British post-punk rock band formed in the late 1970s. Four rivers in the Garden of Eden (Genesis 2:10–14): Pishon (perhaps the Jaxartes or Syr Darya), Gihon (perhaps the Oxus or Amu Darya), Hiddekel (Tigris), and Prat (Euphrates). There are also four years in a single Olympiad (duration between the Olympic Games). Many major international sports competitions follow this cycle, among them the FIFA World Cup and its womens version, the FIBA World Championships for men and women, and the Rugby World Cup. There are four limbs on the human body. Four Houses of Hogwarts in the Harry Potter series: Gryffindor, Hufflepuff, Ravenclaw, Slytherin. Four known continents of the world in the A Song of Ice and Fire series: Westeros, Essos, Sothoryos, Ulthos. Each Grand Prix in Nintendos Mario Kart series is divided into four cups and each cup is divided into four courses.