We all know that Bar Hebraeus described the destruction of the library of Alexandria by the Moslems, and we have seen a very similar story at somewhat greater length given by the Moslem writer al-Qifti translated for us yesterday.
Quite by accident I have come across a mention of an example where Bar Hebraeus displays knowledge of al-Qifti’s book On Learned Men. It’s in Shlomo Pines An Arabic version of the Testimonium Flavianum (1971), which I came across while scanning and throwing out old articles and sat down to read a few minutes ago. I had, in truth, forgotten how mind-numbingly dull that paper was, interesting tho the subject is. But then I reached the appendix on p.73, Galen on Christians, according to Agapius. This reads as follows (bits in  are me):
In a portion of a book bearing the title Galen On Jews and Christians [Oxford, 1949, p.15-6, 57f., 87-98], Professor Walzer treats of a text attributed to Galen by some Oriental, Moslem, and Christian authors, which refers very favourably to the Christian way of life. All these authors but one state that the text occurred in Galen’s summary of Plato’s Republic. The single exception is Bar Hebraeus, who both in a Syriac and in an Arabic work tells us that the text is extracted from Galen’s summary of the Phaedo. …
[Walzer:] “… it is almost certain that the substitution of the Phaedo for the Republic is due to Bar Hebraeus’ notorious carelessness in such matters and of no significance whatever. In addition, Bar Hebraeus is by no means an ‘independent witness’, since his discussion of Galen’s life is nothing but an abridged copy taken from the History of Learned Men by Ibn al-Qifti (published after 1227 C.E.), who, again, attributes the statement to Galen’s summary of the Republic. Bar Hebraeus can therefore be eliminated from future discussions of this statement.”
If we know that Bar Hebraeus was excerpting material from al-Qifti, then we may reasonably suppose that the passage about the library of Alexandria has a similar provenance, surely?