Longtermism is the view that positively influencing the long-term future is a key moral priority of our time.
Longtermism may be seen as following from the conjunction of three key claims. First, future people matter morally. Second, the vast majority of people that will ever exist, if Earth-originating intelligence is not prematurely extinguished, exist in the future. Third, people alive today can predictably influence whether these people exist, and how well their lives go.
Strong longtermism holds that positively influencing the long-term future is the key moral priority of our time. This form of longtermism was introduced by Hilary Greaves and Will MacAskill, and has precedents in the work of Nick Bostrom, Nick Beckstead, and others. Note that the authors do not define or discuss "weak" longtermism; the contrast is rather with longtermism as such, which as noted above holds that positively influencing the long-term future is a key priority, but not necessarily the top priority.
This distinction can be explained in reference to the hinge of history hypothesis, i.e. the hypothesis that we are currently living at a time where humanity has unusually high influence over the long-term future. Urgent longtermists find the hypothesis plausible and, accordingly, hold that it makes sense to spend our altruistic resources relatively quickly. (Altruistic resources include not just financial assets, but other resources that can accumulate and be spent deliberately in the pursuit of altruistic goals, such as credibility, career capital and coordination ability.) By contrast, patient longtermists hold that the opportunities for influence are not concentrated in the near term and, in line with this, they favour investing these resources so that they can be deployed at some point in the future, when the moments of significant influence arrive.
This distinction was originally introduced by Nick Beckstead in his doctoral dissertation, On the Overwhelming Importance of Shaping the Far Future. Targeted (or narrow) longtermism attempts to positively influence the long-term future by focusing on specific, identifiable scenarios, such as the risks of misaligned AI or an engineered pandemic. By contrast, broad longtermism tries to have a long-term influence by pursuing general approaches with the potential to be useful in a broader range of contexts, such as building effective altruism or promoting global cooperation.
Both patient and urgent longtermism, and broad and targeted longtermism, are positions that exist on a continuum. The terms "urgent"/"patient" and "broad"/"targeted" divide these continua into two discrete regions, similarly to how the terms "tall" and "short" divide the height continuum. These distinctions may thus be seen as uncovering an underlying dimension along which longtermism can vary. Accordingly, the more relevant questions are "How patient/urgent should longtermism be?" or "How broad/targeted should longtermist interventions be?", rather than "Should longtermism be patient or urgent?" or "Should longtermism be targeted or narrow?"
One additional distinction sometimes made—which also originates in Greaves and MacAskill—is between axiological and deontic longtermism. ("Axiological" and "deontic" are technical terms borrowed from moral philosophy: "axiological" means "related to what is good or valuable" and "deontic" means "related to what we ought to do or have reason to do".) Axiological longtermism holds that positively influencing the long-term future is among the most valuable things we can do, whereas deontic longtermism holds that positively influencing the long-term future is among the things we have most reason to do. Sometimes these views are combined with strong longtermism, so axiological strong longtermism becomes the view that influencing the long-term future is the most valuable thing to do and deontic strong longtermism becomes the view that influencing the long-term future is the thing we have most reason to do.
Another relevant distinction, introduced by the philosophers Johan Gustafsson and Petra Kosonen, is between normative and prudential longtermism. Normative longtermism is longtermism as it is normally understood, i.e. as a view about what is valuable, or we have reason to do, from an impersonal or moral perspective. However, one can also consider a form of longtermism focused on what is in a person's self-interest. If humans could live for thousands or millions of years, it could be argued that, even from a self-interested perspective, each person should focus primarily on the long-term effects of their actions, because a person's lifetime wellbeing will be largely determined by those effects....