The history of all approved apparitions shows that the Church requires unequivocal evidence of supernaturality. This can be cures, as at Lourdes and Beauraing, or a supernatural prodigy, as at Fátima. The reason from the Church's mystical theology is that most mysticism (as both St. Thomas Aquinas and St. John of the Cross teach) is mediated by the angels (who have a created angelic nature). What the good angels can do the bad angels can imitate, so that many so-called "supernatural" phenomena are merely preternatural (above human nature, but not above the angelic nature). At Garabandal this would include the ecstasies, the ecstatic walks, the returning of rosaries and medals to the proper owners and so on. None of these things, much less the miraculous photos, rosaries turning gold etc. of more recent alleged apparitions, proves anything to the Church about the divine origin of a phenomena. In the absence of some clear supernatural proof neither the local bishop or Rome is likely to approve an apparition.
While two commissions convened by bishops of Santander, Spain, have stated that there were no phenomena which would authentic the events as certainly supernatural they did not condemn the message. In this regard, the first commission stated, "we have not found anything deserving of ecclesiastical censure or condemnation either in the doctrine or in the spiritual recommendations that have been published as having been addressed to the faithful." The bishop who called the second commission, Bishop del Val, upon retiring from office stated in an interview that the message of Garabandal was "important" and "theologically correct." Indeed, some of the prophetic elements of the message can be found in private revelations which have been approved since the initial decision on Garabandal in the 1960s. For example, the concept of a worldwide warning can be found in the Diary of Saint Faustina (Diary n.83), and both the message of Divine Mercy given to her (Diary n.1588), and that of Akita (approved by the local bishop), speak of chastisement if mankind does not ultimately repent. Similar prophetic content can be found in the writings of Elizabeth Canori-Mora and Mary of Jesus Crucified, both of whom were beatified by Pope John Paul II, as well as in prophecies given by God to Blessed Anna Maria Taigi and St. Caspar del Bufalo. Finally, the principal promoter of Garabandal, Joey Lomangino, testifies that it was Saint Padre Pio who told him the Blessed Virgin was appearing at Garabandal and he should go.
It seems, therefore, that notwithstanding the decisions of two commissions accepted by the bishops of Santander, that there are reasonable grounds for individual Catholics to find Garabandal credible. The children themselves predicted that the message of Garabandal would be approved with difficulty, but in sufficient time to spread it. Perhaps this means that the "warning" (a clearly supernatural event) must occur first for approval to be given. Given the seriousness of the times we do well to heed the message of conversion, whether proposed by Fátima or some other source such as Garabandal, Medjugorje or another, without fear, that is, with complete confidence in God's providence for us and the world. The future will take care of itself if we remain spiritually prepared for anything. This has always been the advice of the saints, anyway.
Answered by Colin B. Donovan, STL
There is always the possibility that authentic phenomena can be mixed in with demonic tricks and illusions. These non-approved apparitions are like minefields for ordinary Catholics.