The Torah writes: "When you build a new house, you shall make a fence for your roof, and you shall not place blood in your house, should the one who falls fall from it" (Devarim 22:8). What does the fence accomplish? Will it really save someone, or will its absence really cause someone’s death if it is Divinely decreed that he should either live or die? This dilemma is actually one of the applications of a major, theological question. To what extent is one’s fate affected by natural acts of precaution and to what extent it is determined only by direct Divine Providence? (See Rashi, ad loc. & Sefer Hachinuch #545).

But whatever approach we take on that important issue, the Torah seems to put a lot of stress in this mitzva on the house. "When you build a new house." Halachically, it doesn’t have to be new (Shulchan Aruch, Choshen Mishpat 427:1)!? "You shall not place blood in your house." Why not write that one should not be responsible for another’s death? "Should the one who falls fall from it." Obviously we are talking about falling from it? Why not mention what will happen to him if he falls?

It is likely that the Torah is stressing that the point of making a fence for the roof is more than a precautionary step to prevent tragedy. Rather, building the fence helps define the house. When one builds the fence, the house is as if new, even if it has been standing for decades. It is a house that transmits outwards that life has value and must be safeguarded. It is the potential for falling off, as much as any eventuality, Heaven forbid, which makes a house lacking precautions "a bloody house."

In this way, the fence and any other elements of safety that exist in the house are parallels to the mezuzah. The mezuzah is a sign that the house must protect those within from spiritual dangers, trying to ensure that all that enters the doorway conforms to the basic truths of our religious foundations. So too, the fence exhibits a concern for the physical welfare of those who live in the house or come to visit there.

The two concerns must go hand in hand. The spiritual concern is not sufficient if one does not have a healthy respect for the gift of life. But the world’s strongest and safest fortress is not of true value if it does not allow one who is safeguarded in it to live his life in a significant manner.