The Philosophy Book

80

JUST BY THINKING

ABOUT GOD WE CAN

KNOW HE EXISTS

ST. ANSELM (1033–1109)

IN CONTEXT

BRANCH

Philosophy of religion

APPROACH

Platonic-Aristotelian

BEFORE

c.400 CE St. Augustine of

Hippo argues for God’s

existence through our grasp

of unchanging truths.

1075 In his Monologion,

Anselm develops Augustine’s

proof of God’s existence.

AFTER

1260s Thomas Aquinas

rejects Anselm’s Ontological

Argument.

1640 René Descartes uses a

form of Anselm’s Ontological

Argument in his Meditations.

1979 American philosopher

Alvin Plantinga reformulates

Anselm’s Ontological Argument

using a form of modal logic

to establish its truth.

A

lthough Christian thinkers

believe as a matter of faith

that God exists, in the

Middle Ages they were keen to

show that God’s existence could

also be proved by rational argument.

The Ontological Argument invented

by Anselm—an 11th-century Italian

philosopher who worked on the

basis of Aristotelian logic, Platonic

thinking, and his own genius—is

probably the most famous of all.

Anselm imagines himself

arguing with a Fool, who denies

that God exists (see opposite). The

argument rests on an acceptance

of two things: first, that God is

“that than which nothing greater

can be thought”, and second,

that existence is superior to

non-existence. By the end of the

argument the Fool is forced to

either take up a self-contradictory

position or admit that God exists.

The argument has been accepted

by many great philosophers, such as

René Descartes and Baruch Spinoza.

But there have been many others

who took up the Fool’s side. One

contemporary of Anselm’s, Gaunilo

of Marmoutiers, said that we could

use the same argument to prove that

there exists somewhere a marvellous

island, greater than any island that

can be thought. In the 18th century

Immanuel Kant objected that the

argument treats existence as if it

were an attribute of things—as if I

might describe my jacket like this:

“it’s green, made of tweed, and it

exists.” Existing is not like being

green: if it did not exist, there would

be no jacket to be green or tweed.

Kant holds that Anselm is also

wrong to say that what exists in

reality as well as in the mind is

greater than what exists in the

mind alone, but other philosophers

disagree. Is there not a sense in

which a real painting is greater

than the mental concept the painter

has before he starts work? ■

We believe that

You [God] are that

than which nothing

greater can be thought.

St. Anselm