The difficulties under which this theory labours are mainly these:--
1. It depends on an identification of Clopas with Alphæus, which is uncertain, though not improbable.
2. It depends on a further identification of Christ's "mother's sister" with "Mary the wife of Clopas" in John xix. 25, which is both uncertain and highly improbable. In that verse we almost certainly have four women, and not three, contrasted with the four soldiers just mentioned (vv. 23, 24), and arranged in two pairs: "His mother, and His mother's sister; Mary the wife of Clopas, and Mary Magdalene."
3. It assumes that two sisters were both called Mary.
4. No instance in Greek literature has been found in which "brother" (ἀδελφός) means "cousin." The Greek language has a word to express "cousin" (ἀνεψιός), which occurs Col. iv. 10; and it is to be noted that the ancient tradition preserved by Hegesippus (c. A.D. 170) distinguishes James the first overseer of the Church of Jerusalem as the "_brother_ of the Lord" (Eus. _H. E._ II. xxiii. 1), and his successor Symeon as the "_cousin_ of the Lord" (IV. xxii. 4). Could Hegesippus have written thus if James were really a cousin? If a vague term such as "kinsman" (συγγενής) was wanted, that also might have been used, as in Luke i. 36, 58; ii. 44.
5. In none of the four lists of the Apostles is there any hint that any of them are the brethren of the Lord; and in Acts i. 13, 14, and 1 Cor. ix. 5, "the brethren of the Lord" are expressly distinguished from the Apostles. Moreover, the traditions of the age subsequent to the New Testament sometimes make James the Lord's brother one of the Seventy, but never one of the Twelve, a fact which can be explained only on the hypothesis that it was notorious that he was not one of the Twelve. The reverence for this James and for the title of Apostle was such that tradition would eagerly have given him the title had there been any opening for doing so.
6. The "brethren of the Lord" appear in the Gospels almost always with the mother of the Lord (Matt. xii. 46; Mark iii. 32; Luke viii. 19; John ii. 12); never with Mary the wife of Clopas; and popular knowledge of them connects them with Christ's mother, and not with any other Mary (Mark vi. 3; Matt. xiii. 55). "My brethren," in Matt. xxviii. 10, and John xx. 17, does not mean Christ's earthly relations, but the children of "My Father and your Father."
7. But the strongest objection of all is St. John's express statement (vii. 5) that "even His brethren did not believe on Him;" a statement which he could not have made if one of the brethren (James), and possibly two others (Simon and Judas), were already Apostles.
The identification of James the son of Alphæus with James the Lord's brother must therefore be abandoned, and we remain with three disciples bearing the name of James from which to select the writer of this Epistle--the son of Zebedee, the son of Alphæus, and the brother of the Lord. The father of Judas, not Iscariot, need not be considered, for we do not even know that he ever became a believer.
In our ignorance of the life, and thought, and language of the son of Zebedee and the son of Alphæus, we cannot say that there is anything in the Epistle itself which forbids us to attribute it to either of them; but there is nothing in it which leads us to do so. And there are two considerations which, when combined, are strongly against Apostolic authorship. The writer does not claim to be an Apostle; and the hesitation as to the reception of the Epistle in certain parts of the Christian Church would be extraordinary if the letter were reputed to be of Apostolic authorship. When we take either of these Apostles separately we become involved in further difficulties. It is not probable that any Apostolic literature existed in the lifetime of James the son of Zebedee, who was martyred, under Herod Agrippa I., _i.e._ not later than the spring of A.D. 44, when Herod Agrippa died. That any Apostle wrote an encyclical letter as early as A.D. 42 or 43 is so improbable that we ought to have strong evidence before adopting it, and the only evidence worth considering is that furnished by the Peshitto. The earliest MSS. of this ancient Syriac Version, which date from the fifth to the eighth century, call it an Epistle of James the Apostle; but evidence which cannot be traced higher than the fifth century respecting an improbable occurrence alleged to have taken place in the first century is not worth very much. Moreover, the scribes who put this heading and subscription to the Epistle may have meant no more than that it was by a person of Apostolic rank, or they may have shared the common Western error of identifying the brother of the Lord with the son of Alphæus. Editors of the Syriac Version in a much later age certainly do attribute the Epistle to the son of Zebedee, for they state that the three Catholic Epistles admitted to that version--James, 1 Peter, and 1 John--are by the three Apostles who witnessed the Transfiguration. The statement seems to be a blundering misinterpretation of the earlier title, which assigned it to James the Apostle. And if we attribute the letter to the son of Alphæus we get rid of one difficulty, only to fall into another; we are no longer compelled to give the Epistle so improbably early a date as A.D. 43, but we are left absolutely without any evidence to connect it with the son of Alphæus, _unless_ we identify this Apostle with the brother of the Lord, an identification which has already been shown to be untenable.[18]