The Hinge of History Hypothesis: Reply to MacAskill (Andreas Mogensen)

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This paper was originally published as a working paper in August 2022 and is forthcoming in Analysis.


Some believe that the current era is uniquely important with respect to how well the rest of human history goes. Following Parfit, call this the Hinge of History Hypothesis. Recently, MacAskill has argued that our era is actually very unlikely to be especially influential in the way asserted by the Hinge of History Hypothesis. I respond to MacAskill, pointing to important unresolved ambiguities in his proposed definition of what it means for a time to be influential and criticizing the two arguments used to cast doubt on the claim that the current era is a uniquely important moment in human history.


Some believe that the current era is a uniquely important moment in human history. We are living, they claim, at a time of unprecedented risk, heralded by the advent of nuclear weapons and other world-shaping technologies. Only by responding wisely to the anthropogenic risks we now face can we survive into the future and fulfil our potential as a species (Sagan 1994; Parfit 2011, Bostrom 2014, Ord 2020).

Following Parfit (2011), call the hypothesis that we live at such a uniquely important time the Hinge of History Hypothesis (3H). Recently, MacAskill (2022) has argued that 3H is “quite unlikely to be true.” (332) He interprets 3H as the claim that “[w]e are among the very most influential people ever, out of a truly astronomical number of people who will ever live” (339) and defines a period of time as influential in proportion to “how much expected good one can do with the direct expenditure (rather than investment) of a unit of resources at [that] time” (335), where ‘investment’ may refer “to both financial investment, and to using one’s time to grow the number of people who are also impartial altruists.” (335 n.13) MacAskill thus relates the truth or falsity of 3H to the practical question of the optimal time at which to expend resources to achieve morally good outcomes, considered impartially.

MacAskill presents two arguments against 3H. The first is an argument that the prior probability that we are living at the most influential time in history should be very low, because we should reason as if we represent a random sample from observers in our reference class. The second is an inductive argument that we should expect future people to have more influence over human history because the overall trend throughout human history is for later generations to be more influential.

In my view, neither of these arguments should convince us. As I argue in section 2, MacAskill’s priors argument relies on formulating 3H in a way that does not conform to how this hypothesis is traditionally understood. Moreover, I will argue in section 3 that MacAskill’s definition of what it means for a time to be influential leaves too many unresolved ambiguities for his inductive argument to work.

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