Question: Is it correct to infer from the fact that Avraham is the father of all mankind that all the nations must become Jewish?
Answer: Rashi, in his commentary on the Torah (Bereshit 17:5), hints at this very question. Avraham's name was originally "Avram" which is an acronym meaning "the father of Aram." This means that he was a national leader, the father of his nation, Aram. Later, however, his name (and together with it his mission) was changed to "Avraham" which indicates his universal task as "the father of the multitude of nations." A remnant of his former name remains in his new name which shows that despite his new universal character, he still retains his national character. He is both universal and particularistic. This is not an anomaly: the Kuzari (2:36) says "Israel is the heart of the nations." Or, as the Zohar puts it, "the mind of the nations" (Zohar, Mishpatim 108. See Orot Yisrael of Rav Kook 1, 1). The comparison to the essential limbs, the heart and the mind, indicates that Israel is on a different level of existence from the rest of mankind, which could be compared to inessential parts of the body, such as the leg or the ear. We are the central life force present of humanity. But we must remember that the heart only has significance when it is connected with the rest of the body - not as a detached organ sitting in isolation.
We are inextricably linked to the rest of the nations and have a responsibility towards them, but at the same time we are also distinct and separate from them. Along with them, we possess the Divine image that exists in mankind, but we are above them from our external vantage point, "as a Nation that will dwell alone, not counting itself among the nations" (Bamidbar 23:9). We must use our special characteristics to help them. This state of connection and separateness can be exemplified by the world of ideas. There are ideas that are common to both Jews and non-Jews and it makes no difference if they were conceived by Aristotle or, on a completely different level, by the Rambam. These ideas are broad concepts, well beyond national distinctions. A second category of thought is one where the idea is universal but the style in which it is stated is specific to each nation. Therefore, they have to be specially adapted to our specific national style before they can be adopted. This is unlike the first category that can be adopted without any alterations. There is a third class of ideas which are distinctly ours. Regarding them, we are "as a Nation that will dwell alone, not counting itself among the nations." These ideas are specifically ours and have no connection whatsoever with the non-Jews. This example in the sphere of ideas also applies to the practical world. We and our forefather Avraham are one and act identically. Avraham was connected to the nations as "the father of the multitude of nations," but also a "mighty nation" (Bereshit 12:2), naturally separated from the nations and also a source of blessing to them. In the same way, we are both nationalistic and universalistic, and a source of blessing for the entire world.