Kaplan believed that the Jews were among the first to make a religion of their peoplehood. He was a life long Zionist and believed that Zionism was an essential part of being Jewish. But most importantly, he strongly differentiated between the religion of ancient Israel and collective egotism or what we today would call nationalism.
Loyalty to the Jewish people ideally means accepting the collective ideals of justice and mercy, law and order, and a responsibility to mankind. Loyalty in and of itself can be an admirable quality, but Kaplan knew that in the case of a collectivity or our national selves, it is often just another way of talking about self-interest. He believed that Judaism, both here and in Israel, however, offered a perfect means to overcome the egotism of the self. Judaism projects onto God the ideals of the collective mind; these ideals are then manifested in daily conduct, appearing in Jewish tradition in the form of mitzvot.
As Kaplan puts it,
“The people of Israel, however, did not merely deify their patriotism but subordinated it to a divinity of cosmic proportions. They thereby subordinated it to principles which are coextensive with the cosmos – the principle of law, order and from the standpoint of human functioning, also responsibility to or for mankind.”
From Mordecai M. Kaplan, Soterics- A ReligiousHumanism Unpublished. MSS. RRC Archives, page 200