Ephesians 2:20 reads “built on the foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone.”
There is a debate as to whether we have two groups of people (apostles and prophets) or only one (apostles-prophets or apostles who are also prophets). The latter view is defended by Wayne Grudem. While Grudem offers a number a reasons to support his position, one of them is the grammatical construction on the text. To be clear he does not say the construction requires his view but that it is a “grammatically acceptable” reading of the Greek. It is on this point that some have taken issue. We have in this passage the article “kai” prior to the first noun (“apostles”) but absent from the second noun (“prophets”). Grudem contends this construction can mean that we have one group of people in view. Scholars have raised doubts about the legitimacy of Grudem’s position when the passage contains two plural nouns. D.A. Carson notes, “His list of more than twenty examples where a single article governs two substantives that have the same referent includes few instances of two plural nouns in this array. . .” (Showing the Spirit, 96n.73. Emphasis his.)
Daniel Wallace in his Greek Grammar Beyond the Basics writes, (TSKS in the quote stands for “article-substantive-kai-substantive.”)
“Our point is simply that the syntactical evidence is much against the ‘identical’ view, even though syntax has been the primary grounds used in behalf of it. As we have seen, there are no clear examples of plural nouns in TSKS fitting the ‘identical’ group in the NT, rendering such a possibility here less likely on grammatical grounds.” In a footnote Wallace says, “In Grudem’s study he mixed singular TSKS constructions and plural participial TSKS constructions in with Eph 2:20. But the semantic patterns of each of these constructions do not match noun+noun plural TSKS constructions: There are no clear examples of plural nouns displaying identity, while all singular and virtually all plural participles fit this category.” (285n.82)
Peter O’Brien in his commentary on Ephesians says it is “questionable syntactically.” (The Letter to the Ephesians, 215) Whatever other merits Grudem’s position has Clinton Arnold says Grudem’s view has not “proven persuasive” and notes that he is “not aware of any commentators who have accepted this view.” (Ephesians, 169 and 169n.73) Most commentators see either two different groups or one group being a subset of the other. Wallace concludes that the most probable meaning is that the passage is speaking of “the apostles and [other] prophets.” (286)
For Grudem’s full defense see his book The Gift of Prophecy in the New Testament Today. Again, to be fair to Grudem his case is not built on the syntax alone but on several other items of evidence. I’m only focusing on this part of the argument which seems to be fairly weak.