I noticed that the greek aorist verb ôphthê used in 1 Cor. 15:5-8 to denote the appearance of Christ to Cephas, the twelve, the 500 bretheren, James and all the apostles, and Paul in verses 5-8 are in the indicative mood and passive voice.
Jeffrey A. Rydberg-Cox, Overview of Greek Syntax states regarding aorist verbe in the indictative mood that *The aorist or imperfect indicative stands in the protasis of past contrafactual conditions. The aorist or imperfect indicative with an stands in the apodosis.*
Rydberg also says that *The imperfect indicative stands in the protasis of present contrafactual conditions.*
Rydberg points out that *The passive voice denotes that the subject is acted upon.*
A contrafactual is A statement or other linguistic construction expressing an idea that is presupposed to be false, as I would go in the sentence I would go if I could.
Protasis refers to the clause expressing the condition in a conditional sentence, in English usually beginning with if.
Apodosis is the clause expressing the consequence in a conditional sentence, often beginning with then, as “then I will” in “If you go, then I will.”
Since ôphthê as used in 1 Cor. 15:5-8 asserts contrafactual conditions standing as protasis without corresponding apodosis, the appearances cannot be taken literally. Instead the author clearly meant the perception of Christ to be an invitation to religious drama by virtue of employment of the passive voice wherein the subjects are acted upon. The reader too, by faith, can partake of the ôphthê of Christ and become the corresponding apodosis of religious drama. The other use of protasis was as a component of ancient Greek drama followed by epitasis, catastasis, and catastrophe. The ancients were well acquainted with Greek drama and grammar. They would have implicitly understood the grammatical metaphor of aorist-indicative-protasis to the opening action of a religious drama. That this makes it quite likely that the author of 1 Cor. 15:5-8 actually meant to assert that members of the audience could partake of Christ via an envisioning through religious ecstasy seems reasonable.