The National Society of Professional Engineers maintains a Code of Ethics which opens with the fundamental canon that engineers shall, “Hold paramount the safety, health and welfare of the public.” Structures, tools and other features of the built environment may be designed with what is known as “operational morality,” meaning that care has been taken to ensure that both the construction process and the final product are safe. I have been studying issues of machine morality this summer for a new responsum on halakhah and autonomous vehicles, but for today, my focus is on building safety, specifically during the course of construction.
Parashat Ki Teitze contains the following instruction: “When you build a new house, you shall make a parapet for your roof, so that you do not bring bloodguilt on your house if anyone should fall from it” (Deut. 22:8; JPS trans). As is their habit, the sages of Israel take this single verse both deep and wide. They seek to define its parameters—does it refer only to new construction, or also to purchasing or renting an existing structure? Does it matter if the building is singly or jointly owned? If it is intended for private or public use? How high and how wide must a structure be before this obligation is invoked? Practical answers to all of these questions are found in the early midrash (Sifre Devarim, #229), and Talmud Yerushalmi (Sukkah) and Bavli (Sukkah, BM, BB etc.). If there is any reasonable expectation that a person might use the roof, and any danger that they might fall, then it is the responsibility of the builder, owner, or renter to install a sturdy and effective barrier to protect people from danger.
Our sages go further, comparing this verse to a passage in Exodus (21:33-34) which likewise addresses public safety: “When a man opens a pit, or digs a pit and does not cover it, and an ox or an ass falls into it, the one responsible for the pit must make restitution; he shall pay the price to the owner, but shall keep the dead animal.” With this comparison, the sages have expanded the Torah’s concern from the narrow one of building a parapet to the much broader issue of public safety. In b. Ketubot 41b, Rabbi Natan asks, “What is the source for the rule that a person should not maintain a vicious dog, or keep a shaky ladder at home? It is the verse (from our portion), “so that you do not bring blood-guilt in your house.” The parapet is just an example of the broader principle—both the building and that which it contains must be made as safe as possible. Continue reading