At the same time, he attended Brooklyn College, where he received a Bachelor of Arts degree in history, summa cum laude.

In 2020, Greenberg joined the faculty of the non-denominational, liberal-leaning Yeshivat Hadar as the Senior Scholar in Residence.

He has taught extensively, and a number of well-known scholars, including Rabbi Joseph Telushkin and Michael Berenbaum, consider him their mentor.

He sees the Jewish people's covenant with God as enjoining them to set an example for the moral edification of humanity.

Another concept is his idea that the image of God in all humans implies that each person has "infinite value, equality, uniqueness".