I am very intrigued by the last in a series of essays on Chanuka in R. Norman Lamm’s Festivals of Faith: Reflections on the Jewish Holidays (ed. David Shatz, OU Press, RIETS, New York, 2011, pp. 189-90), entitled “On the Threshold.” He notes that Shabbat 22a decides in favor of R. Shmuel MiDifti that the Chanukiya should be located on the left of the doorpost as one enters the home, on the side opposite to where the Mezuza is placed. According to R. Lamm, this sets the Mitzvot of the Chanuka lights and Mezuza apart from other Commandments, in that they are made functions of the structure in which one lives, rather than one’s person, i.e., Chovat Binyan instead of Chovat Gavra.
As a rationale for these two Mitzvot that are designed to be placed at a “threshold ” over which one has personal control—it is the place where you live because you either own or rent it–R. Lamm launches into a reflection about the significance of the doorway that separates “inside” from “outside.” He notes that this distinction is already implied in God’s Words to Kayin following his disappointment over his sacrifice not being accepted, while his brother Hevel’s was Deemed appropriate by HaShem: