Suppose there is a plausible model of the atmosphere in which global warming will lead to the extinction of humankind unless the consumption of fossil fuel is reduced drastically. Even though the probability of this outcome is small or indeterminate, it is in some hard-to-explicate sense a 'real' one. The implications for action seem compelling: even if the use of fossil fuel has many indubitable benefits, it ought to be curtailed drastically. No finite gain can outweigh the 'real' possibility of the extinction of humankind. On reflection, however, this conclusion is too quick. For suppose there is also a plausible socioeconomic model in which reduced use of fossil fuel leads to global economic collapse, which leads to nuclear war and to a nuclear winter that causes the extinction of humankind. Now, what do we do?

Readers of this volume are likely to recognise the structure of Pascal’sWager and of the many-gods objection to Pascal’s argument. In this chapter I try to reconstitute some of the context of Pascal’s Wager and to assess the validity of the argument. I carefully say ‘some’ of the context, as the theological debates in which Pascal’s argument is embedded are highly complex and well beyond my expertise. Although I have been greatly assisted by Leszek Kolakowski’s acute and irreverent God Owes Us Nothing, I do not claim that standing on his shoulders enables me to see as far as he did.