To many Protestants, “Marian apparitions” and appearances of the other saints are all either frauds or demonic occurrences.* If this describes how you feel, consider this–this view is both (1) Bibically untenable and (2) calls into question every small “o” orthodox opinion Protestants hold.
*To be fair, Got Questions takes a more tempered view, allowing for the possibility of appearances, but warning we must compare what is taught by these alleged saints by the Scriptures.
1. Post-death appearances occur in the Scriptures and early Jewish writings. We have the appearance of Elijah and Moses on the mount of transfiguration, the two witnesses in Revelation are often considered the same two men by Protestant theologians, and the early Jewish writing 2 Maccabees speaks of an appearance of Onias (a deceased high priest) and Jeremiah in a “vision.” In short, to say every appearance after death is demonic contradicts the Scriptures and forces an extra-biblical hermeneutic upon the Scriptures (i.e. unless the appearance is recorded in the Scriptures, it is demonic by default).
2. Protestants, like the Orthodox, have largely the same Christological doctrine and Biblical Canon (sans some Old Testament books). Both the Canon and Christological doctrine we have in common was hammered out in the fourth century. We must be careful to reiterate it is not that the beliefs we share did not precede this period of time, as they are Apostolic teachings given to the Apostles by God Himself. Nevertheless, the terminology we use to describe it (i.e. Trinity, Godhead, Hypostasis, essence, substance, etcetera) are all terms that are used in formulations from between the third and fourth centuries. We, both Protestants and Orthodox, are comfortable with these formulations and have stuck with them for 1700 years because they are the best we can come up with.
That being said, the same men whom we trust to have accurately hammered out the Christological details in creedal statements and theological treatises–many of the same men of whom were the first to agree upon a 27 book New Testament that both Orthodox and Protestants share–had no problem believing in appearances of Mary and the other saints. For example, in the third century Saint Gregory the Wonderworker devised a Trinitarian Creedal statement (“…There is a perfect Trinity, in glory and eternity and sovereignty, neither divided nor estranged. Wherefore there is nothing either created or in servitude in the Trinity…”). This creedal statement was, allegedly, given to him by no other than Mary herself. This story is not passed down to us in some medieval “lives of the saints,” but by another pivotal Trinitarian apologist from the century subsequent, Saint Gregory of Nyssa
The earliest appearance of a saint after death we have is that of Polycarp, the associate of the Apostle John. It is documented for us in the Martyrdom of Polycarp, a writing that liberal textual-critics date to the mid second century
The above should not be taken as license to believe every single story about an appearance of a saint. In fact, there are demons who masquerade as saints, angels of light, and etcetera. However, what we do have is proof that apparitions are part of Christian history and the Scriptures, and cannot be handwaved away outright as demonic in all circumstances. If we do that, we put our shared Scriptures and doctrines into question.