Saving Life: Pikuah Nefesh

Climate change is life-threatening on a massive scale. Among the predicted effects over the 21st century are significantly more frequent and severe droughts and floods. These are events that, at their worst, can kill millions. 1 Some credible analysts claim that the Darfur genocide, which has already killed over 800,000 is partly a consequence of sharpened competition for land and water caused by climate change.2If so, such lethal conflicts over dwindling vital resources will only increase as the problem grows more severe. The medium range projections predict hundreds of millions of climate change refugees from 2050 onwards, as large swathes of tropical lands become all but uninhabitable.3 The likely loss of life in such mass migrations is scarcely imaginable.

Saving life is a cardinal Jewish principle. The Torah teaches that humans were created, “in the image of God, (Genesis 1:26). Each person partakes in the divine and is therefore of infinite value.

A famous mishnah states:

“Therefore, man was created as an individual, to teach that if anyone destroys a life, it’s as if he has destroyed a whole world; and anyone who saves a single life, it’s as if he has saved a whole world.” 4

Each human being is likened to a whole world, of infinite value and irreplaceable uniqueness.

This being so, the Torah requires us to take assiduous precautionary measures to prevent the needless loss of human life.? The archetype for this requirement is the commandment to build a protective parapet around the roof of your house to prevent people from falling off and hurting themselves: “When you build a new house you shall make a parapet for the roof, and you shall not bring bloodguilt on your house.” (Deuteronomy 22:8).

In his authoritative code of halakhah, Maimonides generalizes from this mitzvah to other cases of potentially lethal danger:

“…so too for any case where there’s a danger that a person may unwittingly die from…there is a positive obligation to remove the danger and to be extremely careful about it…and if he neglects to do so and leaves impediments that can cause danger he has negated a positive commandment and violated “he shall not place blood guilt on his house.”5

The Torah does not allow us to court danger and hope for the best. We cannot count on God to save us if we are stupid or negligent. The author of Sefer Hahinukh makes this clear in his explanation for the commandment to build a parapet around a roof:

“God created His world and based it on natural foundations. He made fire to burn and water to extinguish fire. So too, if a large stone falls on a person’s head, it will crush his brains and if he falls from the top of a high roof to the ground, he will die. The Merciful One,…breathed a living, intelligent soul into humans, so that they might save themselves from harm.” 6

It is not faith, but foolishness to dice with death and expect God to help. Divine mercy consists not in bailing us out of any danger that we bring upon ourselves, but in giving us the wit and wisdom needed to avoid the danger in the first place.

Today we call these “natural foundations” of the world scientific laws. If the best available scientific evidence shows that human actions are causing climate change that is likely to lead to massive loss of life, then the Torah clearly requires us to take whatever action we can to avert that threat. 7 This is so, even if there is still a small measure of doubt about the science. Given the immense risks and dangers of delay, the precautionary principle derived from the mitzvah to build a parapet requires that we take action now.

It is interesting to compare and contrast this argument with the findings of the Stern Review. Sir Nicholas Stern, Chief Economic Adviser to the UK Treasury calculated that the cost of taking effective action to avert climate change would be about 1% of global GDP. Against this, he estimated that the cost of not taking action and dealing with the consequences of serious climate change would be somewhere between 5% and 20% of global GDP. 8

It is certainly reassuring to know that investing now in preventing climate change later is extremely cost-effective. However, from a halakhic angle this is beside the point. Investing now is likely to save countless lives, and that is more than enough justification for doing so.

1 See Campbell et al. The Age of Consequences: The Foreign Policy and National Security Implications of Global Climate change, 24, Washington DC, 2007 for a discussion of the likely orders of magnitude involved.
2 See for example,,,2217393,00.html
3 Campbell 2007
4 Sanhedrin, 4:5. The standard printed versions of this text include the word “b’yisrael,”implying that the mishnah is only speaking of saving or destroying Jewish lives. The scholar Ephraim Urbach proved conclusively that the original versions of the mishnah did not include this interpolation; the mishnah was in fact speaking of all human life. See Urbach in Tarbiz 40, 1971, 268-84.
5 Maimonides, Hilkhot Rotzeah V’shemirat Nefesh. 11:4.
6 Sefer Hahinukh, 538. The author goes on to say that for a small number of saintly individuals, God may suspend natural consequences to save them from seemingly inevitable peril.
7 A leading Israeli posek Rabbi Yaakov Wahrhaftig told me in conversation that taking action on climate change is obviously an issue of pikuah nefesh, saving life.