A 'fact of history' is a truth for everybody, believers, sceptics or unbelievers. The Battle of Bannockburn took place quite independently of any belief or doubt one might have as to its occurrence; it is a matter of evidence not of perception.

A 'truth for believers' is either a truth demonstrable to everyone else as well or it is a perception on the part of believers alone. The Incarnation is clearly a perception - albeit one that many good and wise people feel deeply compelled to entertain - while many others feel compelled to discount it.

For one thing, the very existence of a god cannot be proved and theologians have mostly ceased to claim that it can; to believers, God is a notion they choose to believe in or are accustomed not to question. For another, there is some reason to think that the Jesus of the gospels is a legendary construction based perhaps on some less extraordinary historical reality.

If the two parties to the perceived Incarnation are both, at best, honestly or compulsively held perceptions then any connection between them must, of necessity, be more a matter of subjective belief supported by rationalisation than of historical fact based upon evidence. If believers are to be given the respect they deserve they should not make it hard for the rest of us to accord them that respect. The churches have been digging their own graves for long enough by their presentation of the gratuitously improbable as the essentially true, by valuing 'simple' conformity more than free enquiry.