Anselm of Canterbury in the context of "Pope Paschal II"

Intentionality is the mental ability to refer to or represent something. Sometimes regarded as the mark of the mental, it is found in mental states like perceptions, beliefs or desires. For example, the perception of a tree has intentionality because it represents a tree to the perceiver. A central issue for theories of intentionality has been the problem of intentional inexistence: to determine the ontological status of the entities which are the objects of intentional states.

An early theory of intentionality is associated with Anselm of Canterbury's ontological argument for the existence of God, and with his tenets distinguishing between objects that exist in the understanding and objects that exist in reality. The idea fell out of discussion with the end of the medieval scholastic period, but in recent times was resurrected by empirical psychologist Franz Brentano and later adopted by contemporary phenomenological philosopher Edmund Husserl. Today, intentionality is a live concern among philosophers of mind and language. A common dispute is between naturalism, the view that intentional properties are reducible to natural properties as studied by the natural sciences, and the phenomenal intentionality theory, the view that intentionality is grounded in consciousness.

Christian apologetics (Ancient Greek: ἀπολογία, "verbal defense, speech in defense") is a branch of Christian theology that defends Christianity.

Christian apologetics have taken many forms over the centuries, starting with Paul the Apostle in the early church and Patristic writers such as Origen, Augustine of Hippo, Justin Martyr and Tertullian, then continuing with writers such as Thomas Aquinas, Duns Scotus, William of Ockham and Anselm of Canterbury during Scholasticism.

In the philosophy of religion, an ontological argument is a deductive philosophical argument, made from an ontological basis, that is advanced in support of the existence of God. Such arguments tend to refer to the state of being or existing. More specifically, ontological arguments are commonly conceived a priori in regard to the organization of the universe, whereby, if such organizational structure is true, God must exist.

The first ontological argument in Western Christian tradition was proposed by Saint Anselm of Canterbury in his 1078 work, Proslogion (Latin: Proslogium, lit. 'Discourse [on the Existence of God]'), in which he defines God as "a being than which no greater can be conceived," and argues that such a being must exist in the mind, even in that of the person who denies the existence of God. From this, he suggests that if the greatest possible being exists in the mind, it must also exist in reality, because if it existed only in the mind, then an even greater being must be possible – one who exists both in mind and in reality. Therefore, this greatest possible being must exist in reality. Similarly, in the East, Avicenna's Proof of the Truthful argued, albeit for very different reasons, that there must be a "necessary existent".

The existence of God is a subject of debate in the philosophy of religion and theology. A wide variety of arguments for and against the existence of God (with the same or similar arguments also generally being used when talking about the existence of multiple deities) can be categorized as logical, empirical, metaphysical, subjective, or scientific. In philosophical terms, the question of the existence of God involves the disciplines of epistemology (the nature and scope of knowledge) and ontology (study of the nature of being or existence) and the theory of value (since some definitions of God include perfection).

The Western tradition of philosophical discussion of the existence of God began with Plato and Aristotle, who made arguments for the existence of a being responsible for fashioning the universe, referred to as the demiurge or the unmoved mover, that today would be categorized as cosmological arguments. Other arguments for the existence of God have been proposed by St. Anselm, who formulated the first ontological argument; Thomas Aquinas, who presented his own version of the cosmological argument (the first way); René Descartes, who said that the existence of a benevolent God is logically necessary for the evidence of the senses to be meaningful. John Calvin argued for a sensus divinitatis, which gives each human a knowledge of God's existence. Islamic philosophers who developed arguments for the existence of God comprise Averroes, who made arguments influenced by Aristotle's concept of the unmoved mover; Al-Ghazali and Al-Kindi, who presented the Kalam cosmological argument; Avicenna, who presented the Proof of the Truthful; and Al-Farabi, who made Neoplatonic arguments.

Augustinianism is the philosophical and theological system of Augustine of Hippo and its subsequent development by other thinkers, notably Boethius, Anselm of Canterbury and Bonaventure. Among Augustine's most important works are The City of God, De doctrina Christiana, and Confessions.

Originally, Augustinianism developed in opposition to Pelagianism; it was widespread in medieval western philosophy until the arrival of Thomism and Aristotelianism.

The Proslogion (Latin: Proslogium, lit. 'Discourse') is a prayer (or meditation) written by the medieval cleric Saint Anselm of Canterbury between 1077 and 1078. In each chapter, Anselm juxtaposes contrasting attributes of God to resolve apparent contradictions in Christian theology. This meditation is considered the first-known philosophical formulation that sets out an ontological argument for the existence of God.

The original title for this discourse was to be Faith Seeking Understanding.

The satisfaction theory of atonement is a theory in Catholic theology which holds that Jesus Christ redeemed humanity through making satisfaction for humankind's disobedience through his own supererogatory obedience. The theory draws primarily from the works of Anselm of Canterbury, specifically his Cur Deus Homo ('Why Was God a Man?'). Since one of God's characteristics is justice, affronts to that justice must be atoned for. It is thus connected with the legal concept of balancing out an injustice.

Anselm regarded his satisfaction view of the atonement as a distinct improvement over the older ransom theory of atonement, which he saw as inadequate, due to its notion of a debt being owed to the devil. Anselm's theory was a precursor to the theology of later theologians like John Calvin, who taught the idea of Christ suffering the Father's just punishment as a vicarious substitute.