In an unrelated question, some users started arguing about the existence of Geber (Jabir ibn Hayyan - جابر بن حيّان) from 806−816 AD and pseudo-Geber (probably from 13th-14th century). This discussion led to the manipulation of some Wikipedia entries adding the claim that Geber may have or have never existed.
To clear up the issue, I wanted to ask, is there some evidence about his historicity (as a person)? To what extent do we know about him?
See Lawrence Principe, The Secrets of Alchemy (2013, The University of Chicago Press), page 33-on for Jabir and the Jabirian Corpus:
"a person who played as large a role in Arabic alchemy as Zosimos did in the Greco-Egyptian—one Jabir ibn-Ḥayyan. Or, to speak more accurately, several Jabir ibn-Ḥayyans. Or perhaps none at all. A persistent problem facing historians of alchemy is figuring out if an author really is who he says he is, and if he lived when and where he claims."
And see page 55:
"the most influential of these 13th-century Latin alchemical compositions appeared under a very familiar name, that of Jabir, rendered in medieval Latin spelling as Geber. Thus, the “Jabir problem” discussed in the previous chapter had yet another dimension: whether the Latin books known under the name of Geber were translations of Jbir, or whether they were native Latin productions. Historians of science argued vociferously over whether Geber was really Jabir. Recent scholarship has settled the issue: he was not. Geber was a late thirteenth-century Latin author."
"The author concealed behind the pseudonym of Geber is probably an Italian Franciscan friar and lecturer named Paul of Taranto. [Footnote. We owe this identification, and the solution to the “Jabir-Geber” problem,to the painstaking studies of William R. Newman. For a detailed treatment of Geber’s identity, see Newman, “New Light on the Identity of Geber,” Sudhoffs Archiv 69 (1985): 79–90, and “Genesis of the Summa perfectionis,” Archives internationales d’histoire des sciences 35 (1985): 240–302. For an edition, translation, and historical contextualization of the Summa, see Newman’s The Summa Perfectionis of Pseudo-Geber.]"
All serious scholars of science or history of science should realize that Wikipedia has a long way to go to become a reliable source of scientific history, especially if it is about very ancient personalities. Article written by people under nicknames or pseudonyms and of sometimes of dubious credibility have little value for researchers. Afterall, who are the authors of those entries? We have no clue. If we start believing whatever appears on Wiki or Stack Exchange all academic history departments in universities will become redundant and they should shut down.
Besides other historians, consult the work of Syed Nomanul Haq, Names, Nature and Things, Springer Link from the Center for Middle Eastern Studies, Harvard University. Another highly respected historian of Jabir is P. Kraus, who is extensively referenced in his book. Kraus also learned Arabic and consulted original bodies of Arabic works. I am not sure if the chemist turned historian, Lawrence Principe, learned ancient Arabic to consult original works. There is no evidence from his CV.
Haq agrees that not all the 3000 pieces of can be attributed to one person. Of course, there is no doubt that one Jabir Ibn Hayyan existed. Just like botanical and zoological nomenclature of species, it is hard of match trinomial or tetranomial ancient Arabic names, so the point of having many Jabirs is useless.
The problem is what is attributed to him as his body of work (Stigler's law of eponymy) is true or not. Likewise we can question if Pythagorous theorem is his actually his or not? Did Euclid write all the books? Common problem with ancient texts, but should not doubt if Euclid existed or not. Otherwise, skepticism has no limits.
The author writes
${ }^{1}$ In the Jabirian treatises which have either been published or read by me in manuscripts, as well as in the traditional biographies, the patronymic part of the author's name (kunya) appears frequently as Abū Mūsa, but sometimes also as Abū 'AbdAllāh. Often attached to it is the epithet al-Süfi, the tribal name (nisba) al-Azdĩ and names indicating Jäbir's place of origin al-Kūfi or al-Tūsī. Ibn Khallikān (d. $681 / 1282)$ reports in his Biographical Dictionary that Jäbir was from Tarsūs (see de Slane tr. [1842-71], I, p. 300$)$ and this is confirmed by another standard source, the Kashf al-Zunūn of Häjji Khalifa (d. $1069 / 1658)$. However, this latter biographer - according to whom Jäbir died in $160 / 777-$ calls him al-Tarsūsi at one place, but at another place says that Jäbir was from Tarsūs and is called al-Tūsi (!) (see Flügel ed. [1835-1858], p. 34 and p. 79). Ibn al-Nadim, who in naming Jäbir wavers between both kunyas, Abū Mūsa and Abū 'AbdAllāh, mentions the belief that Jäbir was originally from Khurāsān (see Flügel ed. [1871], pp. 354-358).
