Yahya is correct that the Scriptural terminology doesn't use the word "person" or "being" or show a differentiation between the two. However Perkins has not shown the word "person" or "being" is applied to the Father anywhere in the Bible either. Clearly not only does a differentiation not exist, but the words themselves are not mentioned! Hence Perkins must also be guilty of violating sola scriptura if Yahya is correct. But that is a questionable assumption itself because I haven't found a definition of "Sola Scriptura" that says that we cannot infer distinctions in persons or beings or infer such conceptions given our language, in fact it seems this concoction of Yahya's was far from the intent of the pioneers of such doctrine. We could obviously say that the being/person of the Father is not the same person/being as Yahya (John), yet that differentiation isn't made explicitly anywhere, yet it is still obviously true that Yahya does not share the same person or being as the Father. Also it is not at all clear how 'extra biblical material' cannot be used as a yard-stick to interpret the Bible given that any language the Bible exists in, has pre-defined terminology, we must learn the language, linguistic and meaning, before attempting to interpret anything. It is therefore in fact impossible to interpret the Bible without a yardstick given from the basis of the science of linguistics or philosphy of language itself.
Ijaz presumptive claim that the vast majority of doxologies are added is a non-sequitor. Even if that were the case, the distinctions of being and person can still be ascertained (the personhood of the F, S HS are distinct) without such doxologies. It is not shown how historically Christians were at all wholy dependent on such doxologies to infer distinctions in person or being. This would also be irrelevant to the O.T. (or even largely the Gospels) where such "binitarian/trinitarian" doxologies do not exist yet Trinitarians still infer distinctions based on personhood.
Further more it is not explained why James White has common ground with such assertions (doxologies were developed/added), it would seem highly unlikely White would agree with such a contention, hence it would be irrelevant to his own set of interpretative principles. Hence under the interpretive principle of Tota Scriptura, White is perfectly within his right to inteprete accordingly, the Bible as a "whole" unless Ijaz can demonstrate that such a spiritual interpretative tradition is off the hook in a historic theistic tradition, which is dubious.
Ijaz claim that "Godhead" is absent from the N.T is just false (Col 2:9), it is an old English term meaning "divinity" and is translated that way in the KJV as such. The claim that person or being is absent is not shown to be important, as even if that is the case, one can infer God is an almighty "being" who is a "person", no more or less could also be inferred about John the Baptist who is also a "person" and a human "being". The claim that it is "read into" or "eisegeted" is therefore dubious, since "inference" is a valid hermenutical methodology that even Unitarians (and even Muslims) themselves enjoy and employ when reading the Bible (and/or Qur'an). For example the Bible never refers to God as a "self" but most conceive of God as a self or a personal agent. A self with consciousness, awareness or a disembodied animating spirit, all possibly valid descriptions. yet none of which are used of God in the totality of Scripture.
Ijaz questions whether Paul had the authority to change or arbitrarily reform the Shema. However Christians in general (who view Paul as possessing such authority and agree with this particular interpretation of Corinthians) are not obligated to assert Paul "changes" the Shema in the sense entailed by Ijaz, but rather he "interprets" or "modifies" the Shema due to it and an older tradition possessing a pre-existing embedded multi-personal notion of God as either recorded in the judeo tradition or revealed in the relevant recent history by the Lord Jesus Christ. Paul's views are also in perfect accordance and conjunction with the interpretive methodology and principles of the Hellenistic Judaism of his period. In addition we would expect given the anticipated progressive revelation held to by the Jews, who had not argued all revelation was sealed, and this would have to be even more true, due to the recent advent of the Messiah sent to Israel. For example two Scholars report:
"The references to the roles of the Father and of the Lord Jesus Christ in creation (“from whom and through whom”) also reflect traditional scriptural affirmations of the roles of God and of Wisdom in creation (for the latter, see Prov. 8:22–31; Wis. 9:4, 9; Philo, Flight 109). In prophetic literature Yahweh’s absolute power as creator of heaven and earth is what sets him apart from idols, which, on the contrary, are human creations (e.g., Jer. 10:3–16; Isa. 44:9–24). The description of Christ in terms normally attributed to Wisdom (Wis. 8:1–6; 9:1–2, 9; Sir. 24) suggests that just as Jesus takes the place of “the Lord” in the Shema, he also takes the place of “Wisdom” within Hellenistic Judaism: “Paul has indicated that everything one might hope to gain through possessing [sophia (Wisdom)] can be gained rather by possessing Christ” (N. T. Wright 1992: 130)." Beale, G. K., & Carson, D. A. (2007). Commentary on the New Testament use of the Old Testament (pp. 717–718). Grand Rapids, MI; Nottingham, UK: Baker Academic; Apollos.
Or simply read Dr Michael Lakey work.
Hence according to many scholars the only way in which Paul diverges from the Shema (as understood in his time) is by the precise "identification" of the Wisdom/Logos with the historical personage of "Jesus" himself, which is truly unique. The Logos is no longer merely God's creative principle, but is revealed in a historical person, the Messiah of Israel.
The final objection I will address is that the H.S is not mentioned in the Christianized Shema. Personally I find this objection the most persuasive, however it would have to be combined with other evidence, by itself it's not compelling enough. For example Paul has some other creeds that omit mentioning the Father "sending" the Son (Phil 2:6-11) in the context of the salvation/restoration of mankind, yet clearly this is an essential part of primitive Christian theology as a whole when it comes to salvation and/or restoration. Nor do any of these creeds mention the H.S at all, let alone as "God", yet despite this obviously the H.S. played a vital role in the view of the early Christians. Do we conclude they rejected the H.S due to it's absence? Or do we conclude, their theological development advanced as they were able to access the increasing knowledge of the totality of Scripture and Tradition? Ultimately this appears to be nothing more than an argument from silence, that needs to be cojoined with other data to be made useful.