Alexander's letters serve also to fix a probable date for Clement's death between 211 and 215 [Veronika E. Grimm, From Feasting to Fasting p. 87]
According to a later letter of the same Alexander to Origen Clement died soon after this, for this second letter, which can hardly be later than 217 and may have been earlier, implies that he was dead. [Hugh Jackson Lawlor Church History p. xlvi]
That is all we know, except that by 216 Alexander refers to him in such a way that he must be dead (Eus. HE 6,14,8 cf. 6,19,16); he is one of "those blessed men who have trodden the road before us." [John Ferguson, Clement of Alexandria p. 16]
We last hear of him in a letter of Alexander to Origen, written in c. 215, in which he is described as "makarios" and "prodeusas" ie, as having died. Consequently, we gather that he must have died around 215 AD. [Peter Karavites, Evil, freedom, and the road to perfection in Clement of Alexandria p 5]
Alexander mentioning Clement in the letter as a "blessed presbyter" whose work has strengthened and increased the church in Eus. HE 6.11.6; and Alexander's subsequent letter (c. 215-6) reporting the death of Clement in Eus. HE 6.14.9. [Everett Procter, Christian controversy in Alexandria: Clement's polemic against the Basilideans and Valentinians p. 34]
Alexander was one of Clement's old pupils, and a fellow-pupil with the great Origen. Clement must have died not long after this letter was written ; for the same Alexander, writing to Origen a few years later, speaks of him together with Pantaenus as " those blessed men who have trodden the road before us." [G. W. Butterworth Clement of Alexandria p. xii]
Eusebius tells us of a letter composed by Clement's student Alexander, delivered by Clement to the church in Antioch sometime in 211. However, in a letter to Origen dated somewhere around the year 215, Alexander indicates that both Pantaenus and Clement had passed away, suggesting Clement's death to be some time prior to that date. [Andrew C Itter, Esoteric teaching in the Stromateis of Clement of Alexandria p. 7]
In any case, Clement does not appear to have lived much longer after his trip to Antioch. A second letter by Alexander, this time written to Origen around 216, indicates that Clement had died: "For we know well those blessed fathers who have trodden the way before us, with whom we shall soon be;w Pantsenus, the truly blessed man and master, and the holy Clement, my master and benefactor, and if there is any other like them." [Carl P. Cosaert, The text of the Gospels in Clement of Alexandria p. 11]
He left Alexandria at some point and reappeared in 211 as the bearer of a letter from Alexander (in Cappadocia), a possible former pupil with whom he may have been staying, to the church at Antioch. Clement's death may be presumed from another letter from Alexander that speaks about him in the past tense. [Andrew G. Traver, From Polis to Empire, p. 100]
It is frequently said that Clement arrived in Alexandria around the year 180 and left there during the persecution of Christians under the emperor Severus in 202, but the only clear evidence we have for the chronology of Clement's life is contained in two letters of Alexander, bishop of Jerusalem, quoted by Eusebius. In the first, written in 211 to the church in Antioch, probably while Alexander was in Cappadocia (central Turkey), he writes: 'I am sending you these lines, my dear brothers, by Clement the blessed presbyter, a man virtuous and whom you have already heard and will now come to know' (HE 6.11.6). The second, written to Origen in 215, presupposes Clement's death. Alexander writes of Pantainos together with 'the holy Clement, who was my master and benefited me, and all others like them. Through these I came to know you, who are the best in all things, and my master and brother' (HE 6.14.9). Taken together, these letters suggest that Clement left Alexandria no later than the year 211 and died some time between 211 and 215. At the time Alexander writes, the word 'presbyter' could mean either priest or bishop. [Paul Foster, Early Christian Thinkers: The Lives and Legacies of Twelve Key Figures p. 70]
As I have noted here many times already there is nothing in the account of Eusebius that makes any sort of conclusive statement about the death of Clement. Foster has the right general idea about the ambiguity of the testimony of Eusebius, but in my opinion 'cops out' at the last minute with respect to the date of his death.
Indeed Migne and Biggs correctly note that nothing can be conclusively established about any of these details:
A partir de ce moment, l'Histoire ecclésiastique ne fait plus mention de lui; on ne sait s'il resta à Antioche ou s'il retourna soit à Jérusalem , soit à Alexandrie. On ignore, comme nous l'avons vu, jusqu'à la date précise de sa mort. [Jacques-Paul Migne, Troisième et dernière Encyclopédie théologique: Volume 54 p. 123]
How long he continued in Alexandria, and when and where he died, are all matters of pure conjecture. The only further notice of Clement that we have in history is in a letter written in 211 by Alexander, bishop of Jerusalem, to the Antiochians, and preserved by Eusebius (HE vi. 11) ... It is conjectured that he went to his old pupil Alexander, who was at that time bishop of Flaviada in Cappadocia, and that when his pupil was raised to the see of Jerusslem Clement followed him there. The letter implies that he was known to the Antiochians, and that it was likely he would be still better known. Some have conjectured that he returned to Alexandria, but there is not the shadow of evidence for such conjecture. [Charles Bigg, Encyclopedia Britannica, Vol 6, 1910 p. 488]
In fact when we look at the literature on Clement there are those who argue for almost any date up until the time of Theodore's (= Gregory) conversion to Christianity c. 224 CE. Here are some samples of various dates proposed for the death of Clement in the literature:
It is not known whether he again returned to Alexandria. He died AD 217 [Albert Stöckl, Handbook of the history of philosophy, p. 230]
He lived some time during this period at Jerusalem, (then called iElia Capitolina,) where he became instrumental in confirming and enlarging the Christian church. He afterwards returned to Alexandria, where he appears to have died about 218 AD [Joseph Esmond Riddle, A manual of Christian antiquities p. 94]
Titus Flavins Clemens (Clement of Alexandria) was born about 150, perhaps at Athens, came to Alexandria in 202 or 203 and died there about 219. [Frederick Copleston, A History of Philosophy: Volume 2 p. 26]
Clement of Alexandria, fl. AH 189-219 [Archibald Hamilton Charteris, The New Testament scriptures: their claims, history and authority p. 211]
He is supposed to have died about ad 220 [Alexander Roberts, James Donaldson, Clement of Alexandria p. 12]
Clement of Alexandria, born probably at Athens about 150, AD died at Alexandria 220. [Michael Faraday, Jesus Christ p. 105]
During the persecution by Septimius Severus in 202 he fled, and was in Jerusalem in an. He never returned to Alexandria, but died about 220. This is all that is known of his life. [John Wesley Hanson, Universalism, the prevailing doctrine of the Christian church p. 111]
Clement of Alexandria, who died ad 220 [Biblical notes and queries, Volume 1 p. 273]
Titus Flavius Clemens was born around AD 150 and died around AD 220. [Christopher J. Eppling, A study of the patristic doctrine of free will p. 78]
Clement of Alexandria died about 220 [Christoph Ernst Luthardt, St. John the author of the fourth Gospel p. 44]
Clement of Alexandria (Titus Elavius Clemens), ono of tho fathers of tho church, born probably at Athens about tho middle of tho 2d century of our era, died at Alexandria about 220 [George Ripley, Charles Anderson Dana, The new American cyclopædia Volume 5 p. 332]
Clement of Alexandria (c. 150-c. 220), a convert to Christianity probably born in Athens, taught in Alexandria until around 202 and died in Antioch. [Matthew Webb Levering, On Marriage and Family p. 5]
Clement of Alexandria, the preceptor of Origen, died AD 220 [Adam Clarke, the Holy Bible p. 86]
He died about the year 220 [Joseph Thomas, Universal pronouncing dictionary of biography and mythology: Volume 1 p. 619]
Clemens, Titus Flavius, known as Clement of Alexandria, one of the fathers of the church. ... Died about 220 [Samuel Maunder, William Leist R. Cates, The biographical treasury, a dictionary of universal biography p. 141]
Clement probably moved to Jerusalem about 205 and certainly died before 221. [David Ivan Rankin, From Clement to Origen: the social and historical context of the church fathers p. 125]
It is said that after finishing his work in Antioch, the catechist returned to his school, and died in his native city, 222 AD. This is practically all that we know of the life of [Clement] [Francis Ryan Montgomery Hitchcock, Clement of Alexandria p. 121]
Origen, Clement's successor (c. AD 225), is alleged to have said that Mark wrote his Gospel as Peter explained it to him [Merrill Chapin Tenney, New Testament Survey p. 152]
This father, though older than Tertullian, died three years before him, about the year 207. He himself, he says in the first book of his Stromata, " approached very near the days of the apostles." [François Samuel R. Louis Gaussen, The canon of the holy Scriptures p. 157]
Thus we are distinctly told by Eusebius in the fourth century and by Photius in the ninth, that Clement of Alexandria (died about 213 AD) wrote notes upon all the Catholic Epistles in a lost work of his called the Hypotyposes [Reginald St. John Parry, Cambridge Greek Testament for Schools and Colleges p. xviii]
I can't believe how flimsy the argument for dating the letter from Alexander referencing the death of Clement is deemed by anyone to be conclusive. Someone could have written these things up to any age after the events in question. There is absolutely no reason to think that we know when Clement died. This opens up the possibility that Clement might well have addressed the Mar Saba to Gregory Thaumaturgus (= 'Theodore') which in turn might open the possibility that something in Gregory's surviving writings might make reference to the contents of the letter.
