Skipping over a few verses (though the skipped verses do mention speaking in tongues), brings this study to the twenty-second verse where Paul writes “So then, tongues are a sign not for believers but for unbelievers” (1 Corinthians 14:22a). What does Paul mean by this? Inevitably, this runs back to the fact that the activity of speaking in tongues, as if possessed by the spirit of a god, is not an uncommon feature of a religiously-oriented assembly and would not be an unexpected component of an association that honored a particular god, as did the Christians.
Offering up some reasonable conjecture, one might be able to propose that those that joined in as observers or casual witnesses of the meal-based Christian assembly, and were thereby placed in a position in which they witnessed such activity, would be aided in their realization that the Christians worshiped a god by the name of Jesus (a god that was crucified and said to be resurrected). Furthermore, in witnessing the nature of the activity around the meal table of the association that honored this god Jesus, whose story was substantially different than that of any other god of which they might be acquainted, the radically different social order (no obvious honor-based distinctions) that was to be on display in the assembly would be inescapable. Finally, when excessive honor was not conferred upon the ecstatic speaker, the unbeliever would be curious as to this diversion from accepted social practices.
The second half of the twenty-second verse has Paul writing “Prophecy, however, is not for unbelievers, but for believers” (14:22b). This, of course, is a speaking forth of the word of the Creator God (generally calling the covenant people or powers-that-be to account for their failures to live up to their respective obligations, and often using veiled language). As usual, one does not approach these particular words independently of, or in isolation from the other mentions of prophecy within the same train of thought, but hears them in the context that has been created for them.
Returning then to the first verse of the chapter, one is reminded of the instruction to “Pursue love and be eager for the spiritual gifts, especially that you may prophesy.” In verse three: “the one who prophesies speaks to people for their strengthening, encouragement, and consolation.” In verse four, “the one who prophesies builds up the church.” In verse five, with a contrast built upon what has been said about the strengthening of the church, one finds “I wish you all spoke in tongues, but even more than you would prophesy,” with the attachment of verse six, which then reads “The one who prophesies is greater,” because the result is “the church may be strengthened.”
Paul has already encouraged them to abound in manifestations of the Spirit of the Creator God for the purpose of strengthening the church (14:12), with that strengthening also encompassing the previously mentioned encouragement and consolation, clearly connected to prophecy, and all of it has been done in the context of pursuing the most-to-be-honored gift of self-sacrificial love that has been highlighted in the thirteenth chapter.