Suppose Anselm's ontological argument worked. Suppose it could be demonstrated, using nothing but commonly available logic, that there must exist a being greater than which nothing could be thought - and that we agreed that this is the being which all call 'God'. Suppose - and a valid ontological argument would yield this result - the existence of such a being were shown to be necessary.
Is this the God of the Bible?
We could ask, is the being described to be identified with the Father, Son and Holy Spirit? Is the being described that same being which is revealed by Jesus Christ?
Let me sharpen it up a little. Suppose we accept that the God we know from Scripture - the God we see revealed in Jesus Christ, and who makes himself known to us in the testimony of the prophets and apostles - could be described as the most perfect being imaginable. Would the converse be true? Could the most perfect being imaginable be described as the God and Father of our Lord Jesus Christ?
I believe the answer is firmly 'no'. In fact, the two 'Gods' being spoken of here have nothing in common. The God of the ontological argument is perfect - but what does this mean in the abstract? Would it include dying in agony on a cross under the curse of God? Could it mean that? When we start from Christ, and then say that God is perfect, that word has content - and the content is Jesus. (Which is just to say, that word is the Word). But if we start from the 'God' of the ontological argument, we start from an empty being - an abstraction, a general and not a particular god - not God.
We are not, then, dealing with another source of knowledge of God which could be coordinated with Jesus Christ; we are dealing with an idol. And the same could be said of any purported knowledge of God apart from Christ. (This could even be said of knowledge derived from Scripture! John 5:39, in context).
Might not this flight into the abstract and general god be the last defence of humanity against the actual God - the God who interferes with my life and my rule over my own world? Might not theism be the last line of defence against Christ?