But what about “spiritual”? The adjective “spiritual” usually indicates a connection with the Holy Spirit, and that would seem to be the case here. But why are the “songs” given this adjective, when the “psalms” and “hymns” are not? Here I discovered that it gets a bit more technical. The nouns “psalm” and “hymn” are grammatically masculine; “song” is grammatically feminine. The adjective “spiritual” is here in its feminine form, to agree with the feminine “song”. So, on the face of it, Paul is indeed describing the songs as spiritual, and only the songs. This seems surprising, especially since he presumably believes that all the Old Testament psalms are profoundly spiritual. So I asked Dr Dirk Jongkind, the editor of the Tyndale House Greek New Testament and an expert on the language. The answer was surprising and counterintuitive: in classical Greek, dating back well before the New Testament or even the LXX were written, masculine would be the default grammatical gender; if the adjective had been in a masculine form, it might have referred to all three nouns. But by the time of the Greek of the New Testament (so-called Koine or “Common” Greek), this distinction did not always apply. Grammatically, the adjective “spiritual” might just apply to “songs”, but equally it might apply to all three nouns. We cannot be sure.
How did scholarship help? In a positive way and a negative way. Positively, it has persuaded me that Paul expected his churches to sing the biblical psalms, and I can think of no reason why that exhortation would not apply to us today. I think it would be hard to demonstrate that he meant only the biblical psalms; but if we don’t sing them at all, it is hard to see how we are obeying these verses. Negatively, it helped me see that we can’t be sure whether the adjective “spiritual” applies just to the “songs” or to all the singing; I am inclined to think it is the latter, but we can’t prove that from the grammar.