[skissane]

There are multiple ethnic groups that follow the Jewish religion – Askhenazim are ethnically quite different from Mizrahim for example – both culturally and genetically. Now, there is some cultural and genetic commonality between the two groups, but is it sufficient to say they are the same ethnicity? Well, Italians and Spaniards traditionally share a religion (Roman Catholicism), speak related languages, and share some biological ancestry – does that make them one ethnic group? From a linguistic perspective, Italians and Spaniards arguably have more in common than Askhenazim and Mizrahim, since Italian and Spanish belong to the same branch (Romance/Italic) of the same language family (Indo-European), whereas Yiddish and Judeo-Arabic belong to completely different language families–Indo-European vs. Afroasiatic–despite sharing influence from Hebrew and Aramaic.

[pavelrub]

> Now, there is some cultural and genetic commonality between the two groups, but is it sufficient to say they are the same ethnicity?

Of course, because both groups view themselves as belonging to the same group of people, with shared customs, history, religion and tradition, that dates back to the Kingdom of Israel. What you don't seem to understand is that ethnicity is a social concept - the criteria isn't "how much two people have in common", but whether a shared identity exists between them. You should ask yourself what makes you refer to both Ashkenazim and Mizrahim as "Jews", and what makes them refer to themselves as such, even among people who don't believe in Judaism.

> Well, Italians and Spaniards traditionally share a religion (Roman Catholicism), speak related languages, and share some biological ancestry – does that make them one ethnic group?

If they share the same ethnic identity then of course.

[skissane]

Ethnicity seems to me to be a sort of taxonomic hierarchy. Some ethnic groups are more closely related to each other than others. Ethnicities can be grouped together into families of closely related ethnicities, which in turn can often be further grouped into broader families of less closely related ethnicities; ethnicities can often be further subdivided into sub-ethnicities. Are Jews a single ethnicity, or a family of related ethnicities? You could ask the same question about the Han Chinese, or about Italians; it is somewhat arbitrary, and the question is influenced by politics – Italian nationalism emphasises the notion of a single Italian ethnicity, separatist movements such as Sicilian nationalism or the Lega Nord emphasise regional ethnic identities instead.

You want to focus on subjective questions of identity, but it isn't clear to me that all Jews have the same subjective sense of identity. Does a secular Zionist in Tel Aviv have the same subjective sense of identity as a Satmar anti-Zionist in Kiryas Joel? Certainly their "subjective sense of identity" has completely different ideological foundations. They likely wouldn't agree on who is a Jew either, since their different ideological foundations would lead them to different positions on issues such as conversion standards and patrilineal descent.

[pavelrub]

Yes - both a secular Zionist Jew in Tel Aviv and a Satmar Jew in the US (both are, by the way, most likely Ashkenazi) would see themselves as belonging to the same broad group of people with shared customs, culture and history - the Jews. This is why we refer to both groups as "Jews".

This doesn't of course mean that their "subjective sense of identity" is identical in its entirety, but that's pretty much the case with every ethnicity.