Sitting in the Chair of Peter

Taking a look at Keating's "Catholicism and Fundamentalism" again, on the topic of Boettner, Keating continues:

Then comes the blooper. Boettner says, "Infallibility is not claimed for every statement made by the pope [true enough], but only for those made when he is speaking ex cathedra, that is, seated in his papal chair, the chair of St. Peter, and speaking in his official capacity as head of the church." At the end of the sentence is an asterisk, which takes the reader to this footnote: "A scientific commission appointed by pope Paul VI in July, 1968, to investigate the antiquity of the 'Chair of St. Peter' . . . reported in early 1969 that the chair dates from the late ninth century . . . ." The point is that Peter's real chair does not exist, so a Pope cannot sit in it. Since, by official decree of Vatican I, he is infallible only when sitting in Peter's chair, he cannot issue infallible definitions at all. The Catholic Church is refuted by its own archaeology!

Boettner entirely misconstrues the meaning of ex cathedra. ...

Or does he? Keating runs on in this same way for a while, but "the Chair of Peter" was construed as a real, genuine chair by Optatus of Mileve, whom Aidan Nichols, in his "The Theology of Joseph Ratzinger," refers to as "Ratzinger's ecclesiological master in the African trio of Augustine's predecessors..." (pg 39).

Here's what Optatus (c. 370) said of "the Chair of Peter":

We must note who first established a see and where. If you do not know, admit it. If you do know, feel your shame. I cannot charge you with ignorance, for you plainly know. It is a sin to err knowingly, although an ignorant person may be blind to his error. But you cannot deny that you know that the episcopal seat ["cathedra"] was established first in the city of Rome by Peter and that in it sat Peter, the head of all the apostles, wherefore he is called Cephas. So in this one seat unity is maintained by everyone, that the other apostles might not claim separate seats, each for himself. Accordingly, he who erects another seat in opposition to that one is a schismatic and a sinner. Therefore, Peter was the first to sit in that one seat, which is the first gift of the Church. To him succeeded Linus. Clement followed Linus. Then Anacletus Clement ... [he gives the list of popes down to his own time]. After Damasus, Siricius, who is our contemporary, with whom our whole world is in accord by interchange of letters in one bond of communion. Do you, if you would claim for yourselves a holy church, explain the origin of your seat. (Cited in Shotwell and Loomis, "The See of Peter," pgs 111-112, writing to the Donatists.)

According to the editors, "not only, he says, was Peter 'head of the apostles' and the first bishop of Rome, but his bishopric at Rome was the first to be established anywhere in the Church. It was the original episcopate. The claim, however, was excessive even for that credulous age. It violated such widely accepted ideas as those of the bishopric of James the apostle at Jerusalem, and of Peter's foundation of the bishopric at Antioch." (111)