Christian philosophy in the context of "The City of God"

Christendom or the Christian world are terms commonly used to refer to the global Christian community, Christian states, Christian-majority countries or countries in which Christianity is dominant or prevails.

Following the spread of Christianity from the Levant to Europe and North Africa during the early Roman Empire, Christendom has been divided in the pre-existing Greek East and Latin West. After the Great schism of 1054, two main branches within Christianity emerged, centred around the cities of Rome (Western Christianity, whose community was called Western or Latin Christendom) and Constantinople (Eastern Christianity, whose community was called Eastern Christendom or Byzantine commonwealth). After the fall of Constantinople in 1453, Latin Christendom rose to a central role in the Western world. Following the reformation, protestantism emerged as the third main branch of Christianity in the 16th century. The history of the Christian world spans about 2,000 years and includes a variety of socio-political developments, as well as advancements in the arts, architecture, literature, science, philosophy, politics and technology.

Christian theology is the theology – the systematic study of the divine and religion – of Christian belief and practice. It concentrates primarily upon the texts of the Old Testament and of the New Testament, as well as on Christian tradition. Christian theologians use biblical exegesis, rational analysis and argument. Theologians may undertake the study of Christian theology for a variety of reasons, such as in order to:

• help them better understand Christian tenets
• make comparisons between Christianity and other traditions
• defend Christianity against objections and criticism
• facilitate reforms in the Christian church
• assist in the propagation of Christianity
• draw on the resources of the Christian tradition to address some present situation or perceived need
• education in Christian philosophy, especially in Neoplatonic philosophy

The perennial philosophy (Latin: philosophia perennis), also referred to as perennialism and perennial wisdom, is a school of thought in philosophy and spirituality that posits that the recurrence of common themes across world religions illuminates universal truths about the nature of reality, humanity, ethics, and consciousness. Some perennialists emphasize common themes in religious experiences and mystical traditions across time and cultures; others argue that religious traditions share a single metaphysical truth or origin from which all esoteric and exoteric knowledge and doctrine have developed.

Perennialism has its roots in the Renaissance-era interest in neo-Platonism and its idea of the One from which all existence emerges. Marsilio Ficino (1433–1499) sought to integrate Hermeticism with Greek and Christian thought, discerning a prisca theologia found in all ages. Giovanni Pico della Mirandola (1463–1494) suggested that truth could be found in many—rather than just Biblical and Aristotelian traditions. He proposed a harmony between the thought of Plato and Aristotle and saw aspects of the prisca theologia in Averroes (Ibn Rushd), the Quran, Kabbalah, and other sources. Agostino Steuco (1497–1548) coined the term philosophia perennis.

Plotinus (/plɒˈtaɪnəs/; Ancient Greek: Πλωτῖνος, Plōtînos; c. 204/5 – 270 CE) was a hellenised Egyptian 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.

The history of logic deals with the study of the development of the science of valid inference (logic). Formal logics developed in ancient times in India, China, and Greece. Greek methods, particularly Aristotelian logic (or term logic) as found in the Organon, found wide application and acceptance in Western science and mathematics for millennia. The Stoics, especially Chrysippus, began the development of predicate logic.

Christian and Islamic philosophers such as Boethius (died 524), Avicenna (died 1037), Thomas Aquinas (died 1274) and William of Ockham (died 1347) further developed Aristotle's logic in the Middle Ages, reaching a high point in the mid-fourteenth century, with Jean Buridan. The period between the fourteenth century and the beginning of the nineteenth century saw largely decline and neglect, and at least one historian of logic regards this time as barren. Empirical methods ruled the day, as evidenced by Sir Francis Bacon's Novum Organon of 1620.