I doubt it.
In the comments in the Rema post below the issue of Karaism and masoretes was raised, so I thought it's an opportune moment to review some of the discussion concerning this matter.
It seems that ever since Simcha Pinsker published his monumental and groundbreaking history of Karaites and Karaite literature Likute Kadmoniot (Vienna 1860) , the following assertion by him was widely accepted as reasonable: when dealing with the grammarians and masoretes (including Ben Asher and BEn Naftali) of the ge'onic period if there is otherwise no indication that they had anything to do with the Talmud then they should be suspected of Karaism, or at least Karaitic leanings, since Rabbanites did not solely occupy themselves with Bible and grammar to the exclusion of Talmudic learning! This applies before R Saadya especially. Of course once Rabbanites began to more closely study the Bible exegetically and grammatically in response to the challenge of Karaism this rule loses it's force, even without evidence that such grammarians engaged in Talmudic learning as well.
So this view was accepted and applied to Ben Asher by Graetz, and accepted ever after (although Aron Dotan notes that O.H. Schorr rightly dismissed Pinsker's axiom as arbitrary in his review of the book):
(Unfortunately the German original of this volume (V) of Graetz's History isn't yet digitally available. Although my German is limited, the popular English translation is insufficient - it is much, much less scholarly, and in this case all the evidence Graetz marshaled is omitted, but it will have to do for an illustration.)
His arguments are that in some texts Ben Asher is titled "מלמד" (see post below!), and that was a Karaite title of the time, Dunash records that Rav Saadya wrote responsa directed against a Ben Asher, whom he did not respect. (Paranthetically, Harry Orlinsky used to say that the authority of Ben Asher over Ben Naftali lies solely on the basis of Maimonides' endorsement - not that this is really true - and really Rav Saadya would have been a better judge, and he would have endoresed Ben Naftali over Ben Asher!) Additionally, Dunash and his students did not mention Ben Asher in their arguments with Menachem and his students, despite being Palestinian and therefore surely familiar with him. They would have done mentioned him, unless they realized he was a Karaite! Finally, a bonafide Karaite (Yehuda Ha-dassi) seems to have thought Ben Asher was a Karaite, judging by the favorable and respectful ways he refers to him.
Other arguments, brought by other scholars, included the evidence found in the treatise Dikduke ha-te'amim (said to be written by Ben Asher), where it seems to be say that all of Tanakh is useful for determining halakhah, not just the Torah.1 This is the Karaite, not Rabbanite view. Additionally, he sometimes uses specifically Karaitic hermeneutical terminology. Finally (and rather lame) is the argument that since the colophon of the Cairo Codex of the Prophets (codex written by Moshe ben Asher) said that it was commissioned by a Karaite, and indeed this codex remained in possession of Karaites, that he himself must have been a Karaite!
Suffice it to say these arguments are insufficient, as Aron Dotan meticulously showed half a century ago in Sinai 41 (his article ? האמנם היה בן-אשר קראי was expanded and published in English as Ben Asher's Creed).
Dotan reviews in detail all the arguments that were made until his time, pro and con. Some of the arguments that Ben Asher was not a Karaite focused on the idea that Maimonides would not have considered him authoritative if he was a Karaite. The insufficiency of this idea on several grounds needn't be stated. More potently, no Rabbanite ever accused Ben Asher of being a Karaite until 1860! Others disputed that the Ben Asher that Saadya argued against was our Ben Asher.
Dotan's work is really well argued, but I will only review his specific objections to Graetz's proofs.
- it can be shown that מלמד was not only a Karaite title, but also a technical term - teacher - also used by Rabbanites
- the fact that Dunash doesn't mention Ben Asher is meaningless. Neither does Menachem (who was not Palestinian and therefore would be unlikely, according to the argument, to know that he was actually a Karaite)
- Ha-dassi's respectful language is not unusual. Fortunately outside of polemics we do find cordial references between Karaites and Rabbanites. The same Ha-dassi also refers to Yehuda Hayyuj and Yonah ibn Janach (known Rabbanites) in a pleasant, cordial way.
- the idea that Ben Asher's expression that the Prophets "complement" the Torah is Karaitic in intent is faulty, since Karaites viewed the Prophets as Torah itself - there was no tripartite division in the Bible for the Karaites. Rather, this is a Rabbanite view. In addition, the Hagiographa is not included here, and that is not a Karaite view. In addition, the issue of halakhah being derived from the Prophets is far more complex than Graetz presents.
In all, Dotan convincingly refutes the contention (originally based on little more than a tantalizing and contrarian assumption) that Ben Asher was a Karaite. Yet prior to his work it was almost a dogma that Ben Asher was a Karaite. For example, Paul Kahle wrote (1956) "We know with certainty that Moshe b. Asherand his son belonged to the community of Karaites and it is therefore very likely that also the other members of the Ben Asher family were Karaites." ("The Masoretic Text of the Bible and the Pronunciation of Hebrew, JJS 7).
We do not know this with certainty.
Finally, a note to potential Karaite readers of this blog (and I know I have such readers): I personally would not mind at all if Ben Asher was a Karaite. It's only a matter of the evidence and arguments for me. For another point of view, see the following post and comment in this post by Nachum::
"Oh, and one more thing- it seems there's a growing number of Orthodox (again, leaning right, not part of any of the categories listed above) who have taken a real interest in Masoretic issues. An offhand reference to Ben Asher and Karaism by a speaker at the conference brought an impassioned reaction from one audience member, for example, and I've been seeing quite a bit of this in recent times. I'm getting the strong feeling that a lot of people are starting to grasp that something's not quite right with the party line ("every letter from Sinai" is just the tip of the iceberg). Lord knows where it will end, especially when combined with the other sentiments above."
I asked what that was about and was told:
"One of the speakers made an offhand reference to the Leningrad Codex as having been written by a Karaite. One audience member (no one was asking questions mid-speech) protested vehemently, and wouldn't let it go, even though it was off-topic and the speaker conceded the point."
1 סדר הנביאים האשמרת התיכונה שלום התורה כמעמד התורה ומורים מהם הוריה כתורה