Alan
Mankind has made many and varied efforts to reach some form of spiritual fulfilment, but most Christians I know will verify that it was God who called them into the knowledge of His presence.
From the outside you can make assumptions and apply whatever labels come to mind,
Your second statement appears to conflict with the first in the sense that from the outside you are making assumptions about 'most Christians I know will verify that it was God' etc. Also this past statement of yours 'I do not think the human mind is capable of comprehending the true nature of God,' appears to nullify both of the above quotes. How do you judge the inner experience of others, whether Christian or non Christian, and decide whether it is 'divine presence' or not, rather than some form of self delusion or the result of religious egotism?
but when you experience God's calling yourself you will come to realise the truth.
It could also be said that when you realise the truth yourself it has nothing to do with experiencing a god's calling. You appear to be making your
self the authority over others.