The latest publication of the Sacred Congregation for the Doctrine of the Faith (the body once known as the Inquisition) seems designed to provide cheap entertainment for atheists. "Norms Regarding the Manner of Proceeding in the Discernment of Presumed Apparitions or Revelations" contains guidelines for deciding whether to validate "apparitions and the revelations often connected with them". While the infidels giggle, those among the theological intelligentsia who insist on the unimportance of superstition for religion and the primacy of practice over doctrines can only despair.

There's little point in rehearsing the reasons why many laugh this off as evidently absurd. In this case, many of the criteria applied to apparitions are perfectly sensible, in so far as the whole enterprise can be seen as sensible. You have to check whether the witnesses display "honesty", "sincerity" and "rectitude of moral life"; that they are free from "psychological disorder or psychopathic tendencies"; that there is no "evidence of a search for profit or gain"; and that the sighting is inspiring "healthy devotion and abundant and constant spiritual fruit".

What's more interesting are the subtler paradoxes of faith that are found in those key tests which maintain the authority of the church to determine truth and doctrine, paradoxes thoughtful believers are well aware of. Sound witnesses are those who show "habitual docility towards ecclesiastical authority". Any revelations offered by apparitions must be of "true theological and spiritual doctrine and immune from error". It is negative evidence against a sighting if any revelations offered in it contain "doctrinal errors attributed to God himself, or to the blessed virgin Mary, or to some saint in their manifestations".

Herein contains what we might call the paradox of revelation, which is confronted by any organised religion that is based on revelation, in whole or part. As its meaning makes clear, you can't have a "revelation" that tells everyone what they already know. The supposed revelations of God to humanity through Christ, or the word of God to Mohammed through the angel Gabriel, had the power they did because they indicated new truths, new directions for followers.

However, having established a religion on those revelations, the teachings revealed through them become non-negotiable, and the ecclesiastical authorities become the arbiters of their interpretation. And so that means no further revelation is admissible if it contradicts what is already believed. Revelation of radical new truths, if accepted as real, thus makes future revelation of radical new truths impossible. To put it another way, what was absolutely valid for the establishing of a religion becomes by necessity invalid once it already exists.

This isn't trivial. Although the Catholic church exists to further God's will on earth, the criteria set out by the Sacred Congregation for the Doctrine of the Faith make it impossible for the church to accept God's will as being anything other than what they already believe. So while in theory entirely subservient to God's will, God's will actually turns out to be subservient to that of the church.

The Sacred Congregation comes so close to seeing what is wrong with this. It says that we must, in assessing the veracity of an apparition, take into account "the possibility that the subject might have added, even unconsciously, purely human elements or some error of the natural order to an authentic supernatural revelation". All it needs to do is take into the account that the church might indeed be such a subject and it would realise it is too fallible to judge the truth of revelation by comparison with what it already believes.

A religion that has a place for revelation therefore must not be dogmatic, sure that it knows God's will. Organised religion, however, is not very good at achieving this required level of open-mindedness, perhaps because it requires a severe restriction of ecclesiastical authority. This runs counter to the baroque institutional hierarchy of the church, which in this case gives different levels of authority to ordinaries, the regional or national Conference of Bishops, the Apostolic See and the universal jurisdiction of the supreme pontiff can intervene. Divine revelation has become the property of a very human collection of committees and experts. The irony is that if God agrees, the rules humans have made for validating his revelations mean that he would not be believed even if he told us.

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