Listen to this morning's class, on R. Hutner's approach to divrei reshut - the realm that is neither obligatory nor forbidden, here.
Follow along with his Iggerot UKetavim, Pahad Yisshak - Shavuot (no. 36), and Pahad Yisshak - Pesah (no. 69).
For further research:
1) Read R. Yitzchak Blau's thorough analysis of this topic, on Yeshivat Har Etzion's VBM website, here.
3) To learn more about the life and thought of R. Hutner, see Steven Schwartzschild's "An Introduction to the Thought of Isaac Hutner" here, Yaakov Elman's "Pahad Yitzhak: A Joyful Song of Affirmation" here, Hillel Goldberg's "Isaac Hutner: A Synoptic Interpretive Biography" here, and Matis Greenblatt's "Rabbi Yitzchak Hutner: The Song Before His Eyes" here.