Self Driving Cars: Killing One to Save the Many Part 2, By Rabbi Chaim Jachter

The Immunization Precedent

The Tiferet Yisrael (to Mishnah Yoma 8:3) writes (in the middle of the nineteenth century) that we are permitted to inoculate ourselves against smallpox even though there is a small chance (he writes that one in a thousand was the prevailing risk in his time) that one may contract smallpox from the inoculation. [1] He argues that we are permitted to assume the small risk in order to avoid the must greater risk of contracting smallpox.

Rav Reiss’ Application of the Tiferet Yisrael to Self Driving Cars

Rav Moshe Navon, one of the founding engineers of the renowned Israeli firm Mobileye explains: [2]

The World Health Organization estimates that approximately 1.25 million people die in traffic accidents around the world every year. They estimate that over 20 million people are injured in traffic accidents around the world every year. These numbers are about to practically disappear, for with the advent of the autonomous vehicle will come the removal of the number-one factor in car accidents: the human. This does not mean, however, that autonomous vehicles will not have to navigate ethically challenging situations: a truck may drop its payload into the road, a person may unexpectedly cross the street, etc., thus forcing the autonomous vehicle to have to decide who will live and who will die.

Accordingly, while there is a very small risk associated with self-driving cars that they might cause someone who might have otherwise lived to die, the introduction of self-driving cars will overall dramatically reduce the terrible carnage that takes place on the world’s roads.

Rav Reiss argues that this is analogous to the Tiferet Yisrael permitting smallpox inoculations in the late nineteenth century. While there may be a small risk associated (in those days) with taking this inoculation, the overwhelming overall benefit both for the individual taking the vaccine and the broader community, permits receiving this vaccine. Similarly, reasons Rav Reiss, the overwhelming benefit brought about by the introduction of self-driving cars definitely justifies and permits undertaking the slight risk that comes along with it.

As Rav Navon concludes his discussion “the sooner autonomous vehicles are on the road and human drivers removed therefrom, the sooner we can start saving literally millions of lives”.

Killing One to the Save the Many – The Dilemma of the Chazon Ish

One dilemma for which a self-driving car will have to program is if it faced the possibility of running over and killing five pedestrians, whether it may divert into the sidewalk and thereby kill one bystander who would have lived had the car not made this diversion.

This question is famously raised by the Chazon Ish. [3] The Chazon Ish [4] (Choshen Mishpat Sanhedrin, no. 25, s.v. VeZeh LeAyein) describes a situation in which a bystander witnesses the release of an arrow (or missile or grenade) aimed at a large group of people. The bystander has the ability to rescue the intended victims by deflecting the arrow; however, if he does so, the arrow will claim a single victim who heretofore was endangered in no way whatsoever.

The Chazon Ish raises the possibility that the bystander should redirect the arrow and cause the death of the one individual in order to save the lives of the many. He writes “perhaps we should make every effort to reduce the loss of Yisrael life as much as possible”. The Chazon Ish explains that one might consider the act of the bystander as fundamentally an act of rescue and not an act of murder.

The Chazon Ish contrasts the arrow case with the aforementioned Yerushami’s case of delivering a victim to bandits to serve the rest of a group. The latter case constitutes a cruel act of delivering someone to his death since the rescue of the rest of the group results only incidentally. However, when deflecting the arrow one is directly preserving the lives of the intended victims and thus the act may be construed as a “Ma’aseh Hatzalah” and not a “Ma’aseh Retzicha.”

The Chazon Ish also suggests that we should be looking to reduce the amount of loss of life as possible. He compares the situation to Lulinus and Pappus who are regarded as being in the highest place in Gan Eden for their sacrifice.

On the other hand, the Chazon Ish notes that deflecting the arrow is worse than handing over a designated victim to bandits threatening a group. In the Chazon Ish’s hypothetical one directly kills an individual while in the scenario described by the Yerushalmi one only indirectly causes the death of the designated individual, by handing him to the bandits.

Thus, the arrow case is both superior and inferior to the Yerushalmi’s bandit case. The Chazon Ish, therefore, leaves the question as inconclusive/Tzarich Iyun.

The Tzitz Eliezer

In the generations subsequent to the Chazon Ish, four leading Posekim resolved the Chazon Ish’s dilemma in favor of refraining from deflecting the arrow. Rav Eliezer Waldenberg (Teshuvot Tzitz Eliezer 15:70) comes down strongly in favor of refraining from an act of murder even if it saves many lives. Rav Waldenberg begins by quoting the bandits case to show that one cannot save the many at the expense of the individual.

The Tzitz Eliezer then cites the words of the Talmidei Rabbeinu Yonah (Avoda Zara 28a) who explain the reasoning behind the “whose blood is redder” [5] argument. According to Talmidei Rabbeinu Yonah, you might argue that since the “redness” of your neighbor’s blood might be “less red” compared to your own, hence your neighbor should be killed and not you. Nevertheless explain Talmidei Rabbeinu Yonah, you must remain passive (Shev V’al Taaseh), [6] for “one is to refrain from doing any sin with one’s own hands.”

On this the Tzitz Eliezer writes, “Rabbeinu Yonah has laid down for us a critical general principle [to illuminate] the guiding principle that our sages have set for us in relating to questions of life and death, and that is to choose to be in a state of passivity (Shev VeAl Ta’aseh). This is true regardless of which side of a scenario we find ourselves; one must remain passive when it is impossible to resolve whose blood is redder, being ever guided by the principle to refrain from doing any sin with our own hands.

With this, the Tzitz Eliezer goes on the attack against the Chazon Ish, explaining that this guiding principle to refrain from sinning with our own hands applies equally whether the scenario is one-against-one or one-against-many. In all cases, one must remain passive (Shev VeAl Ta’aseh). He notes that the arrow scenario is precisely the same as that of a car driving toward a group of people where the driver could change directions to hit an unrelated individual and thus save the multitude. Performing any action that would result in actively (Kum VeAseh) killing someone is impermissible, regardless of the intent to save the many.

The Tzitz Eliezer also argues that this is the position of the Tosafot which appears in Pesachim 25b (s.v. Af) and Sanhedrin 74b (s.v. VeHa Ester). Tosafot elaborate on the Gemara’s rule that one must sacrifice his life rather than kill another (“Yeihareg V’al Yaavor”). The basis for this rule, as we mentioned is in the celebrated phrase, “how do you know that the other person’s blood is not redder than yours?”

Tosafot adds:

“In a situation where one is not actively killing such as if bandits threaten to push someone on a baby to kill it, it appears that one is not required to sacrifice his life instead of cooperating in this terrible deed. The reason for this is that he can claim, “how do I know that the baby’s blood is redder than my blood” since he is merely passively cooperating in the murderous act. [16]

Rav Waldenburg concludes from this Tosafot that he believes that the proper course of action in such deadly situations is simply Shev VeAl Ta’aseh because we simply have no right to act in such circumstances.

Consequently, explains the Tzitz Eliezer, “in the case of the Chazon Ish we must resolutely decide (Lifsok BeHechleiti’ut) to remain passive and not actively divert the arrow.” The Tzitz Eliezer leaves us with the following decisive words: “In any case of certain killing, there is no distinction between the individual and the multitude, for we do not say that the multitude is to be favored.”

Rav Asher Weiss

Rav Asher Weiss (Minchat Asher, Pesachim 28:9) adopts a similar approach noting that it is difficult to comprehend the distinction between a “brutal act” versus a “saving act,” for in the final analysis, “when one kills a person by his own force (Kocho) it is a violation of murder.”

Rav Weiss then offers three possible ways to understand the Chazon Ish’s proposal (paraphrased here): 1) If one were to abstain from diverting the missile away from the multitude, one could be guilty of violating two biblical commandments – “do not stand idly by your neighbor’s blood” and “return [his health] to him” – which demand that one help his fellow man. Perhaps the Chazon Ish is arguing that being in violation of these two commandments, for each and every one of the people in the multitude. However, Rav Asher is not satisfied with this approach noting “And this still needs investigation.”

2) We might look at the arrow case as one in which all of the people, including the individual, would be killed. While this scenario is comparable to the marauders demanding one individual lest they kill the whole group, in which case one is not allowed to hand over an innocent person, one might argue that diverting the missile is an act of saving as opposed to handing over an individual which is an act of killing. [And indeed, in this case where all would be killed, we are certainly obligated to minimize deaths]. Rav Asher notes, though, that it is clear that the Chazon Ish was not talking about such a scenario. “And this needs a lot of investigation.”

3) It seems we can make sense of the Chazon Ish’s proposal to divert the missile if we assume it is diverted passively. That is, one may not actively bend the path of the arrow to kill the individual as this would be considered one’s own force (Kocho), which is a clear violation of killing with one’s own hands (Hariga BeYadayim) and prohibited even to save the many. However, one could conceivably place a “shield” over the multitude such that the arrow would bounce off of it and land on the individual. Placing a shield and deflecting the arrow would only indirectly cause the death of the individual and thus would not be considered one’s own force (Kocho). “And all of this needs a lot of investigation.”

Though Rav Weiss considers three possible ways to affirm the Chazon Ish’s arrow case as an act of saving versus one of killing, ultimately he remains, like the Chazon Ish, inconclusive.

Rav Sha’ul Yisraeli

A tragic situation that occurred in Tyre, Lebanon in the early 1980’s when a large building, where many Israeli soldiers were located, collapsed, killing many but leaving some victims trapped but still alive. There was a larger group who remained alive on lower floors and a smaller group who remained alive on the upper floors. Israeli experts were faced with the dilemma of choosing to save the smaller groups on the upper floors and then not reaching the victims on the lower floors in time to save them. Alternatively, they could destroy the upper floors (and thereby killing those trapped there) and be able to reach those on the lower floor in time to save them.

The Israeli police asked Rav Shaul Yisraeli his opinion and he ruled (Techumin 4:143) “It is absolutely forbidden to save even the many and the prominent, when saving them requires the killing (even the indirect killing) of someone who otherwise would not be killed”. The Israeli police saved the few on the top floor but sadly were not able to reach those on the bottom floor in time to save their lives.

[1]  All Posekim agree with Rav Asher Weiss’ assertion that currently one is obligated to vaccinate themselves and their children in accordance with government regulation.   

[2] http://www.divreinavon.com/pdf/EthicalDilemmasinProgrammingAutonomousVehicles_MoisNavon.pdf

[3]  This ethical-Halachic dilemma is commonly studied in secular settings and is referred to in the secular world as “The Trolley Problem”.  This discussion was introduced by Oxford University Professor Philippa Foot.  However, apparently unbeknownst to Professor Foot, the Chazon Ish had already raised this issue decades beforehand.  

[4]  Rav Anthony Manning reports that this discussion of the Chazon Ish resulted from an actual She’elah asked to him by a taxi driver from Haifa who was driving down a hill when his brakes failed. His car was heading into a group of people and he steered it instead into a single individual who was killed. He wanted to know if he did the right thing. This is reported in a Sefer written by one of the Talmidim of the Chazon Ish - Zecher LeDavid - who was present when the question was posed to the Chazon Ish.   

[5]  Interestingly, Talmidei Rabbeinu Yonah define the Gemara’s poignant term “redder blood” as referring to one who will better serve the Will of Hashem.   

[6]  The notion of Shev VeAl Ta’aseh indicates that the issue is too great for a human being to resolve.  We therefore yield and permit Hashem to take over and determine the proper course of action.  

[7]  The Minchat Chinuch (295-296:23) identifies Tosafot’s assertion with the assertion of Rabi Akiva (Bava Metzia 62a) in the famous case of two people in a desert with sufficient water for only one of them, that one does not share his water with his companion.  The Minchat Chinuch sees Rabi Akiva as saying that one is not required to sacrifice his life to save another’s life if he is passive.  By contrast, Rav Chaim Soloveitchik (to Rambam Hilchot Yesodei HaTorah 5:1) understands Rabi Akiva as limiting the obligation to rescue. Rabi Akiva is teaching that there is no Chiyuv Hatzalah in case where one would thereby lose his life.  


Self Driving Cars: Killing One to Save the Many Part 3 By Rabbi Chaim Jachter

Self Driving Cars: Killing One to Save the Many Part 1 By Rabbi Chaim Jachter