A few years ago I received a phone call asking me to give money to buy the freedom of a slave (in the Sudan). The cost, and sacrifi ce to me, would be extremely modest – no more than $50, or dinner for two. It seemed an incredibly compelling ask. Nonetheless I was reluctant to give, fearing that I would just be reducing the supply of slaves and thereby driving up the “price.” That seemed to me to create the potential to draw more people into the slave trade and thereby increase the number of slaves. My fear was that freeing a slave might result in more than one person being newly enslaved and so make things worse off than they were. With the help of some economists, I found out my intuitions were misplaced. Redeeming the freedom of one slave (under most circumstances) does no harm and likely does at least some good. It turns out if I buy the freedom of 10 slaves, no more than 10 people will be newly enslaved and likely less than 10 will be enslaved. So, all other things being equal, net-net, I do more good than harm by buying their freedom (for details, see Karlan and Krueger 2007). There is a complication in this analysis. It assumes that the costs of slavery can be shared so that two people enslaved for 6 months each is no worse than one person enslaved for 1 year. But that may not be the case. Suppose systematic rape is an accompaniment of the act of enslavement. But suppose we can be sure this complication does not hold. Then ought I not to give? “No” Peter Singer might say, “you can bring about a greater good by giving your money to feed starving people.” (In fact that is just what Singer did say to me about this issue in conversation.)
My goal is to examine the force of this prescription in what follows by applying Singer’s challenge when it comes to the question of avoiding climate change. But in doing so, I fi rst want to examine the problem through the lens of slavery and then extend it to the problem of climate. In this regard, I am going to be
especially interested in focusing on the force of the phrase “might be able to” and in contrasting it to what we are likely to do. The core question I am interested in is this: at least when it comes to doing good, like the act of freeing a slave, even if there are alternatives that would produce greater good, what kind of factors might undermine the likelihood of those alternatives being realized? That is a quick and dirty version of the question that I am interested in. The more proper version is comparative: at least when it comes to doing good, like the act of freeing a slave, even if there are alternatives that would produce greater good, what kind of factors might undermine the comparative likelihood of those alternatives being realized over the likelihood of freeing a slave? One more twist, for we ought to not just worry that the best alternative is less likely to be realized than the second best, but that that comparative likelihood of it happening may be relatively hard to change. At least when it comes to doing good, like the act of freeing a slave, even if there are alternatives that would produce greater good, how robust are the factors that might diminish the comparative likelihood of those alternatives being realized over the likelihood of freeing a slave? So by extension for climate change the question is then this: even if avoiding climate change would produce a greater good as compared to other alternatives, how robust are the factors that might diminish the comparative likelihood of our realizing it over realizing those alternatives?