Thomas Aquinas is widely regarded as the father of Scholasticism, a philosophical and theological movement that dominated medieval thought.

Eudaimonia, often translated as 'happiness' or 'flourishing', is the central concept of Aristotelian ethics, referring to the ultimate goal of human life.

Dialectic, a method of philosophical inquiry involving critical examination of opposing viewpoints, is considered by Plato to be the highest form of knowledge.

Ataraxia, meaning 'freedom from disturbance', is the main ethical principle of Stoicism, emphasizing the importance of inner peace and tranquility.

Anselm of Canterbury, in his 'Proslogion', presented the ontological argument for the existence of God, based on the idea of a 'First Cause'.

The Categorical Imperative, a moral principle formulated by Immanuel Kant, is the central ethical principle of Kantian ethics.

Siger of Brabant is known for his theory of 'double truth', which posited that there can be truths in theology that are different from truths in philosophy.

Hedonism, the pursuit of pleasure and avoidance of pain, is the main ethical principle of Epicureanism.

William of Ockham is known for his theory of 'nominalism', which rejected the existence of universals and posited that only individual things exist.

Ren, often translated as 'benevolence' or 'humaneness', is the central ethical principle of Confucianism, emphasizing the importance of compassion and empathy.

Duns Scotus is known for his theory of 'voluntarism', which posited that the will is the primary faculty of the soul and that God's will is the ultimate cause of all things.

Wu wei, often translated as 'non-action' or 'effortless action', is the central ethical principle of Taoism, emphasizing the importance of living in harmony with the natural order.

Plato is known for his theory of 'exemplarism', which posited that the material world is a reflection of a higher, eternal realm of Forms or Ideas.

Authenticity, the pursuit of living in accordance with one's true self, is the central ethical principle of Existentialism.

Nicolas Malebranche is known for his theory of 'occasionalism', which posited that God is the only true cause and that all other causes are merely 'occasions' for God's actions.