Born and educated in Warsaw, received there Ph.D. in mathematics and so called Habilitation in philosophy. He used to teach mathematics in Poland, and also, in 1988, in New York, and has been involved in scientific research in the field of logic and the philosophy of mathematics.
Since 1997 has been on the faculty of the Department of Philosophy of Warsaw University where he teaches logic as well as philosophy of religion.
Member of “Solidarity” from the beginning in 1980 until 1990, or in its pioneering and underground periods. After 1989 was among founders of the Polish Council of Christians and Jews and of the Polish-Israeli Friendship Society.
Since its creation, Krajewski has been the Jewish co-chairman of the Polish Council of Christians and Jews, and from 1992 to 1998 a member of the executive committee of the International Council of Christians and Jews.
From 1997 to 2006 Krajewski has been a member of the board of the Union of Jewish Religious Communities in Poland.
For many years he was also a member of the International Council of the Auschwitz Camp Museum and Memorial.
Since 1993 has been the Poland consultant to the American Jewish Committee.
From 2007 he has been working in the team preparing a major Museum of the History of Polish Jews in Warsaw.
Author of articles on logic, and on Judaism, Jewish history and Christian-Jewish dialogue (in Polish and in English), as well as books: Poland and the Jews: Reflections of a Polish Polish Jew, Krakow 2005 (in English), and (in Polish): Jews, Judaism, Poland, Warsaw 1997 (in Polish), 54 commentaries to the Torah for even the least religious among us, Krakow 2004, The mystery of Israel and the mystery of the Church, Warsaw 2007, as well as Goedel.s theorem and its philosophical interpretations: from mechanism to post-modernism, Warsaw 2003.
Married to Monika Krajewska, artist and author; they have two sons, Gabriel and Daniel.