RUSS ROBERTS' stimulating online chat with Stanford's Paul Romer, one of the world's leading experts on economic growth, led me to Mr Romer's excellent forthcoming, updated entry [.pdf] on the topic for the Concise Encyclopedia of Economics, where I found this passage:

People are reasonably good at forming estimates based on addition, but for operations such as compounding that depend on repeated multiplication, we systematically underestimate how quickly things grow. As a result, we often lose sight of how important the average rate of growth is for an economy. ... For a nation, the choices that determine whether income doubles with every generation, or instead with every other generation, dwarf all other economic policy concerns.

The fact that we systematically underestimate even the medium-term effect of compounding growth I think severely hobbles our moral judgment about the importance of economic growth relative to other social desiderata. I used to puzzle a great deal over the fact that moral philosophers (as opposed to economists, who are the vanguard) have devoted so little attention to economic growth given the immense, swift improvements in well-being that high rates of growth have delivered wherever they have occurred. The now-well-documented historical record suggests that economic growth has done more for the welfare of humanity than any moral creed or non-economic initiative meant to improve the dignity and quality of human life. So why is there no treatise required of all undergraduates singing growth's praises and setting it out as a moral imperative for all decent peoples?  

My reading in economic history has somewhat allayed my puzzlement. Economic growth has not been given its due in serious works of moral and political thought in part because of our difficulty in comprehending compounding, as Romer says. We simply don't grasp how enormous the effect of small changes can be, even within our own lifetimes.  But I think think the main answer lies elsewhere.

First, long-term growth is radically transformative of society, but it is also so new. Our most important cultural touchstones, however, are very old. For example, most of the developed world remains committed to religious traditions whose origins precede the era of modern growth. Asking our ancient, inherited ethico-religious frameworks to accommodate the phenomenon of modern growth is somewhat like asking a cat to do calculus.

Second, and last, we have laughably poor and partial imaginations. A wary species, it is all-too-easy for us to imagine doom, as Leonardo DiCaprio's new sermonizing vehicle illustrates. But, partly because we don't easily grasp the logic and mechanisms of growth, we are constantly stumped when we attempt to create credible predictions of non-disastrous futures. People who speak of living a millennium, uploading brains into new bodies, or the coming robot labor-market transformation are widely mocked as dreamy and unserious, while those who claim that we're going to run out of food, or oil, or ozone, or dry land are thereby imbued with gravitas. Certainly, these pessimistic claims feel more plausible than the argument that some innovation or other that we cannot now possibly imagine is going to come around the corner and make Leonardo DiCaprio's worries seem quaint. So, in order to do something to stave off armageddon, we plump for (often largely symbolic) growth-reducing policies with nary a thought about the havoc we may thereby be wreaking on our grandchildrens' well-being. 

As Romer writes:

Only a failure of imagination—the same one that leads the man on the street to suppose that everything has already been invented—leads us to believe that all of the relevant [growth-promoting] institutions have been designed and that all of the policy levers have been found.

If we care about people in poorer countries, poorer people in rich countries, our children, our grandchildren, or even ourselves in 50 years, we ought to be looking harder and offering the biggest rewards our societies can muster for the undiscovered levers of growth. Of course, if an expected decrease in growth rates from allegedly forthcoming environmental disasters could be mitigated by some feasible policy, then that's a growth-promoting policy lever, too, and I am most anxious to hear about it. Especially from the strapping Mr DiCaprio.