How Did Anselm of Canterbury Try to Prove That God Exists?

According to Anselm of Canterbury, we can know that God exists by performing an act of right thinking at the limit of human capabilities.

Feb 2, 2023By Viktoriya Sus, MA Philosophy
anselm of canterbury proof god existance


The ontological argument formulated by Anselm of Canterbury is a gem of medieval theology. It is the only explanation of God’s existence a priori. In other words, it is a proof that does not rely on experience but is based solely on our ability to reason.


Unfortunately, this argument is often simplified and depersonalized, altered, and distorted. Its magnificence and strength can be seen only when it is carefully formulated.


Anselm of Canterbury developed the first version of the ontological argument in his early work Monologion. However, he soon became disillusioned with it, and a new and improved version of the proof was included in the Proslogion. Despite some differences, both works answer the following questions: Does God exist, and can it be proven or verified? If God exists, how can this be confirmed? Can our reason perceive the existence of God as a reality?


Who Was Anselm of Canterbury?

josef fromiller virgin mary painting
Virgin Mary is appearing to Anselm of Canterbury, Josef Ferdinand Fromiller, 2008, via WikiMedia Commons.


Anselm of Canterbury (ca. 1033 – 1109) was a famous philosopher and theologian of the Catholic Church. From 1093 he served as Archbishop of Canterbury (England). After his death, he was canonized as a saint.


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Anselm was born into a noble family in or around Aosta in Upper Burgundy (modern-day Italy). Anselm’s father had a stern and cruel character, while his mother was a patient and pious woman.


At fifteen, Anselm wanted to leave to serve in a monastery, but the local abbot refused this desire since Anselm’s father did not give his consent. As a result, the young man suffered great stress, which resulted in him becoming ill. Shortly after his recovery, he gave up his desire to serve God and lived a carefree life for a time.


After the death of his mother, Anselm’s father repented his former unrighteous way of life. He became such a passionate believer that living with him became unbearable for the young Anselm. Anselm left his father’s house at the age of 23.


Anselm then spent a long time in search of himself. After wandering from monastery to monastery and studying at various church schools in France in 1060, the young man moved to Normandy to the abbey of Bec, where he soon became prior and, in 1078, was elected abbot.


Anselm’s Major Works

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St Anselm, Author unknown, late 16th century, via National Portrait Gallery


Anselm of Canterbury is often called “the most luminous and penetrating intellect between St Augustine and St Thomas Aquinas” and “the father of scholasticism.”


Anselm’s writings are both philosophical and theological since the author seeks to present the Christian principles of faith, traditionally perceived as an indisputable truth, in the form of a rational system.


Anselm also analyzes the phenomenon of language, carefully examining the meaning of religious terms. He and thinkers who followed him, such as Pierre Abelard and Guillaume of Conches, were true innovators in Western philosophy in logic, semantics, ethics, metaphysics, and other areas of philosophical theology.


Stylistically, the works of Anselm of Canterbury are presented in two main forms – dialogues and meditations. In his methodology and philosophy, he followed the Platonic rather than the Aristotelian tradition.


The main problem tackled in his work is the relationship between faith and reason. Anselm of Canterbury solved this problem from the standpoint of Augustinianism – “I believe so that I might understand,” that is, faith precedes reason. According to Anselm of Canterbury, reason can clarify the truth contained in the provisions of faith with the help of dialectics. He believed that all truths of revelation could be rationally proven.


How did Anselm of Canterbury Prove the Existence of God and the Reality of Christian Dogma?

monologion illustration
Illustration to St Anselm’s Monologion, Author unknown, via


Anselm’s views developed under the great influence of the teachings of Aurelius Augustine. Following this famous patristic, he also believed that faith must precede knowledge and that it excludes all doubt – as we said, “I believe so that I might understand”.


However, being a man of the 11th century, he could not avoid paying attention to rational knowledge and was influenced by the logic of Aristotle. So, Anselm acknowledged that the comprehension of truth is impossible without reason, based on faith alone. Therefore, even earlier than Thomas Aquinas, he undertook the attempt to rationally prove the existence of God.


Anselm of Canterbury’s Monologion and Proslogion are two of the most important works in the philosophy of religion. In these texts, Anselm provides a proof for the existence of God, which has come to be known as the ontological argument.


In the Monologion, Anselm takes a more deductive approach, starting with the idea that God is perfect and then working backward to prove His existence.


In contrast, the Proslogion starts with the argument that we have a concept of God in our minds and then asserts that it must mean He exists. Both works are highly influential, but the Proslogion is generally considered superior.


There are a few key reasons why the Monologion is considered inferior when compared to the Proslogion:


  1. Anselm’s deductive approach is not as strong as his inductive approach in the Proslogion.
  2. The Monologion relies heavily on analogy and metaphor, while the Proslogion is more straightforward and logical.
  3. The Monologion focuses primarily on ontological arguments for God’s existence, while the Proslogion also includes teleological and cosmological arguments.


Overall, the Proslogion is a more successful work than the Monologion due to its stronger argumentation and greater breadth of evidence. However, both works are important contributions to the philosophy of religion, and anyone interested in the existence of God should read them both.


The Ontological Argument

michelangelo creation of adam painting
The Creation of Adam, Michelangelo, 1508-1512, via the Sistine Chapel


The ontological argument to prove God’s existence formulated by Anselm of Canterbury goes as follows:


  1. God is, by definition, a being than which none greater can be conceived.
  2. God exists as an idea in the mind.
  3. A being that exists as an idea both in the mind and in reality is greater than a being that exists only as an idea in the mind.
  4. Thus, if God exists only as an idea in the mind, then we can imagine something that is greater than God (a greatest possible being that also exists).
  5. We cannot imagine something that is greater than God.
  6. Therefore, God exists.


Philosophers have debated this argument for centuries, with many different interpretations of it. However, Anselm’s version is generally considered to be the most persuasive.


There are a few key points to understanding Anselm’s argument. First, it is important to note that when Anselm talks about God, he is not referring to the Christian God or any other specific deity. Rather, he is talking about a being possessing all the perfections possible. In other words, God is the highest possible being that could be conceived.


cima conegliano god the father painting
God The Father, Giovanni Battista Cima da Conegliano, 1510-1517, via The Courtauld Institute of Art


Second, it is important to understand what Anselm means by existence. For him, existence is not simply a matter of being physically present in the world. Rather, it is a property of beings that makes them greater than those who do not possess it. So, for example, a unicorn does not exist because it doesn’t have the property of existence. However, a human exists because we have the property of existence.


Third, it is important to note that Anselm’s argument is not proof of the existence of the Christian God or any other specific deity. Rather, it is proof of the existence of a being than which none greater can be conceived. So, even if you do not believe in the Christian God, you must still concede that Anselm’s argument is sound.


Fourth and finally, it is important to understand what Anselm means by ‘greater.’ In this context, greater does not simply mean ‘larger’ or ‘more powerful.’ Rather, it refers to anything that makes a being perfect or more complete. So, for example, a being that is more intelligent or more just is greater than a being that is less intelligent or less just.


Opposition to Anselm and His Proof

antonio fernández jesus painting
Jesus Receiving the World from God the Father, Antonio Arias Fernández, 1657, via Museo Del Prado


Even though Anselm’s ontological proof is a great contribution to both theological and philosophical thought, it has attracted a lot of criticism and served as the basis for many disputes. It is the most controversial of all the traditional logical arguments of systematic theology for the existence of God. According to Paul Enns, this argument is the least significant of all the logical arguments for the existence of God, which he considered in his textbook on systematic theology.


Among the opponents and critics of the ontological argument were not only later thinkers but also Anselm’s contemporaries, particularly the monk Gaunilo, who set out his objections in a polemical book with the ironic title Liber pro insipiente (“In Defense of the Fool”). As for later critics, the following thinkers are the best-known objectors to this proof: Thomas Aquinas, David Hume, and Immanuel Kant.


gottlieb doebbler kant portrait
A portrait of Immanuel Kant by Gottlieb Doebbler, 1791, from the collection of the Ostpreußisches Landesmuseum mit Deutschbaltischer Abteilung, via Wikimedia Commons.


For many centuries, the leading theologians and philosophers were almost evenly divided into those who rejected the ontological argument for the existence of God and those who defended it.


However, none of the warring parties achieved a definite victory. This can only be explained by one thing: each group rejected something completely different from what the other defended. It was not a conflict over the same problem that separated them. They fought over different things that they expressed in the same terms. Those who rejected arguments for the existence of God criticized their argumentative form, while those who defended them accepted their implicit meaning.


Most criticism of Anselm’s proof was and is based on the fact that he (as mentioned above) made, in the opinion of his opponents, an unreasonable transition from the idea of God to His existence while missing the connection between these two concepts. However, such claims ignore that perhaps Anselm did not seek to give strictly scientific apologetic proof but wanted to show the natural harmony between faith and reason in prayerful reflection.


Is Anselm of Canterbury’s Ontological Argument Relevant Today?

giovanni bellini feast of gods painting
The Feast of the Gods, Giovanni Bellini and Titian, 1514/1529, via National Gallery of Art


Philosophers and theologians have debated Anselm of Canterbury’s ontological proof of the existence of God for centuries. Some have seen it as a valid argument for the existence of God, while others have critiqued it as being based on faulty reasoning. However, regardless of one’s opinion on the matter, there is no denying that Anselm’s ontological proof is a fascinating argument that is still relevant today.


In recent years, there has been a renewed interest in Anselm’s ontological proof, largely due to the work of philosophers such as Alvin Plantinga and William Lane Craig. These thinkers have argued that Anselm’s proof can be used to show that the existence of God is more than just a matter of personal belief; rather, they contend that it can be shown rationally that God exists.


Whether or not one agrees with this interpretation of Anselm’s proof, there is no doubt that it is a significant argument that continues to be relevant in the philosophical and theological debate over the existence of God.


Although some scholars dismiss this argument or consider it useless, others see it as a timeless contribution to philosophy. One thing is certain: Anselm, by inventing his proof, deeply impacted the course of medieval theology.

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By Viktoriya SusMA PhilosophyViktoriya is a writer from L’viv, Ukraine. She has knowledge about the main thinkers. In her free time, she loves to read books on philosophy and analyze whether ancient philosophical thought is relevant today. Besides writing, she loves traveling, learning new languages, and visiting museums.