Logos (λόγος; from λέγω, Lego, lit. I say ) is a term in Western philosophy, psychology, rhetoric, and religion derived from a Greek word variously meaning "ground", "plea", "opinion", "expectation", "word", "speech", "account", "reason", "proportion", and "discourse". Logos became a technical term in Western philosophy beginning with Heraclitus (c. 535 – c. 475 BC), who used the term for a principle of order and knowledge.

Epoché ("cessation") is an ancient Greek term. In Hellenistic philosophy it is a technical term typically translated as "suspension of judgment" but also as "withholding of assent". In the modern philosophy of Phenomenology it refers to a process of setting aside assumptions and beliefs. Pyrrhonists developed the concept of "Epoché" to describe the state where all judgments are suspended to induce a state of Ataraxia

Metempsychosis (μετεμψύχωσις), in philosophy, refers to transmigration of the soul, especially its reincarnation after death. It is unclear how the doctrine of Metempsychosis arose in Greece. It is easiest to assume that earlier ideas which had never been extinguished were utilized for religious and philosophic purposes. Orpheus have taught that the Soul is divine, immortal and aspires to freedom, while the Body holds it

Arche (ἀρχή) is a Greek word with primary senses "beginning", "origin" or "source of action", and later "first principle" or "element". In the ancient Greek philosophy, Arche is the element and the first principle of existing things. From Arche all things first come to be and into this they are resolved in a final state. This source of entity is always preserved.

Apeiron (ἄπειρον) is a Greek word meaning "(that which is) unlimited," "boundless", "infinite", or "indefinite" from ἀ-, "without" and πεῖραρ, "end, limit", "boundary", the Ionic Greek form of πέρας, "end, limit, boundary". The Apeiron is central to the cosmological theory created by Anaximander, a 6th-century BC pre-Socratic Greek philosopher. Everything is generated from Apeiron and then destroyed by going back to Apeiron, according to necessity.

The Demiurge is an artisan-like figure responsible for fashioning and maintaining the physical universe, according to Platonic, Neo-Pythagorean, Middle Platonic, and Neo-Platonic schools of philosophy. The Gnostics adopted the term Demiurge. The Demiurge itself and the material from which the Demiurge fashions the Universe are both considered consequences of something else. The word Demiurge is an English word derived from Demiurgus, a Latinised from δημιουργός.