Kierkegaard's Arguement for believing in God even through one cannot use Reason to prove God's existence (see my post on Reason alone not being able to prove or disprove God)
[link to philosophy.lander.edu
"An [unknown thing] is an existent thing.
God is an [unknown thing].
God is an existent thing.
The syllogism is of the valid form:
All B's and C's.
All A's are B's.
All A's are C's
In an argument, one gives reasons, grounds, and evidence for the acceptance of a conclusion. Existence must be assumed in the premisses; it cannot be proved. Occasionally, this point is expressed as "Existence is not a predicate."
Consider the following inferences from the Square of Opposition:
All philosophy students are awake ----------> At least one philosophy student is awake.
All unicorns have horns ---------> At least one unicorn has a horn.
If the subject of the conclusion exists and the conclusion is true, then we must have assumed the existence of that subject in the premisses of the argument.
For example, one does not prove Napoleon's existence from his deeds.
An unknown invaded Russia, lost the Waterloo campaign, was exiled to Elba, and so on.
Napoleon is the unknown.
If we tried to prove the existence of God by a posteriori means, then we could never finish listing the events in the natural order. Thus, the proof would be incomplete--we would be anxiously awaiting future events.
Again, existence explains the deeds, but the deeds do not prove existence.
Thus, Kierkegaard says we would be living in suspense until the proof is complete. The proof would hang on future occurrences."