Thanks to William MacAskill's excellent new book on the topic (What We Owe the Future), lots of people are talking about longtermism right now. For those not familiar with the concept, "longtermism" is the ethical view that "positively influencing the long-term future should be a key moral priority of our time." Below are some of my favorite arguments for longtermism, followed by some of my favorite against it. Note that I borrow from Will's book heavily here in the section on arguments ...