SUMMARY OF ANSELM’S ONTOLOGICAL ARGUMENT
LOGICAL TYPES OF PROOF:
o Inductive arguments – no logical necessity for the conclusion to arise from the premises; the conclusion
is only highly probable.
o Deductive arguments – strongest form of logical proof since the conclusion is already contained in the
premises and must follow; if the premises are true, the conclusion is true.
TYPES OF REASONING / METHODS OF GAINING KNOWLEDGE:
o A posteriori – gaining knowledge through empiricism (sense perception); deals with synthetic propositions
o A priori – gaining knowledge through pure reason; deals with analytic propositions
THE ONTOLOGICAL ARGUMENT: DEDUCTIVE A PRIORI PROOF FOR THE EXISTENCE OF GOD
o Purports to be a deductive a priori argument.
o This means we know the premises are necessarily true using a priori reasoning.
o This means the definition of God is treated as an analytic proposition (self-evident).
o And since it is a deductive argument, as we know these premises are necessarily true, the conclusion
that God exists is necessarily true.
ANSELM’S ONTOLOGICAL ARGUMENT: THE TWO VERSIONS
Both versions use the same reasoning of reductio ad absurdum (in premises 3 to 5 below) – where a
hypothesis is raised in order to show the absurdity of its implications.
ANSELM’S 1ST VERSION (PROSLOGION II) 2ND VERSION (PROSLOGION III)
1. The Fool (atheist) agrees we can talk about God. 1. God is the GCB
This shows God exists in the mind As defined before: no greater being can be imagined
2. God is defined as ‘a being than which none 2. We have just proved the GCB exists in reality
greater can be conceived’ (Greatest Conceivable
Being – GCB)
God is the greatest being that can be imagined As proven by Anselm’s first version of the argument
3. We can also conceive of God-being X that exists 3. Suppose the GCB has contingent existence, we
in reality as well as in the mind can conceive of a God-being X that exists
Here Anselm is presenting the hypothetical Here Anselm is presenting the hypothetical
possibility of there being a GCB (in mind) and God- possibility of there being a GCB (contingently
being X (in reality) existing) and God-being X (necessarily existing)
4. BUT consider the definition of the GCB 4. BUT consider the definition of the GCB
Anselm is pointing out the absurdity of the Anselm is pointing out the absurdity of the
5. The GCB must be the God-being X 5. The GCB must be the God-being X
Since reality is a perfection, GCB = X Since necessary existence is a perfection (it is
greater than contingent existence), GCB = X
6. God exists in reality 6. God necessarily exists in reality