You probably think you are rational. Day to day, you try to \u201cmake the best possible use of the information available to you,\u201d as MIT philosopher Brian Hedden PhD \u201912 writes in his 2015 book, \u201cReasons without Persons.\u201d <\/p>\n
If you think you are rational because of how you plan for the future, and change your beliefs over time, however, Hedden will be skeptical. Circumstances change, and when using reason, he thinks, all that matters is the present. Thus, he also writes: \u201cThe requirements of rationality should be impersonal, avoiding reference to the relation of personal identity over time.\u201d<\/p>\n
This is what Hedden calls \u201ctime-slice rationality,\u201d the idea that in applying reason, we exist in little slivers of time and knowledge. There are not permanently reasonable people, just reasonable decisions. <\/p>\n
\u201cWe are temporally extended people with hopefully long lifespans, but we\u2019re made up of lots of different time slices,\u201d Hedden says. \u201cSo there\u2019s me now, me yesterday, me next year. We should think of the locus of rationality as the time slice, not the temporally extended person.\u201d <\/p>\n
Those past versions of you, Hedden thinks, are like teammates in sports: You are connected to them, but not quite the same person. The payoff from viewing things this way, he contends, is a more streamlined and realistic picture of our thinking. <\/p>\n
\u201cTime-slice rationality\u201d helped launch Hedden\u2019s career. Today he is a professor in MIT\u2019s Department of Linguistics and Philosophy and associate dean for MIT\u2019s Social and Ethical Responsibilities of Computing (SERC) initiative. In a nod to his work, let\u2019s examine some time slices from Hedden\u2019s career.<\/p>\n
Falling for philosophy<\/strong><\/p>\n Hedden grew up in Virginia and attended Princeton University as an undergraduate, where he expected to study electrical engineering. But early on in college, he took some philosophy classes \u2014 an introductory course in logic, a history of early modern philosophy \u2014 and liked them. A lot. <\/p>\n \u201cEngineering is still near and dear to my heart, but I really got into philosophy,\u201d Hedden says. <\/p>\n Almost before he knew it, Hedden had found his primary intellectual interest. Upon graduating from Princeton, Hedden spent a year working for an education nonprofit in Nicaragua, but he had already decided on his next stop: graduate school in philosophy.<\/p>\n That led Hedden to MIT. He wanted to study the philosophy of language, and at MIT, the famous linguistics program is part of the same department as philosophy. Hedden applied to the Institute, was accepted, and arrived on campus eager to pursue his chosen field. <\/p>\n Lounge life<\/strong><\/p>\n A funny thing happened to Hedden after he arrived at MIT, however: He stopped studying the philosophy of language. Blame Frank Gehry, the architect. <\/p>\n MIT\u2019s Department of Linguistics and Philosophy is in the Stata Center, which opened in 2004 and was designed by Gehry to have all kinds of common spaces, including double-height lounges. After Hedden started graduate school at MIT, he got drawn into the philosophical discussions happening in these common areas. Before long, he had changed his intellectual focus. <\/p>\n \u201cThis was largely due to conversations that were happening in the lounge,\u201d Hedden recalls. \u201cThe Stata Center has spaces that really encourage collaboration. A lot of people there were talking about puzzles involving probability, epistemology, and decision theory, and I found those things really stimulating, and wound up specializing in those areas. Things wouldn\u2019t be the same if the building were differently arranged.\u201d<\/p>\n Advised by MIT professors Caspar Hare, Robert Stalnaker, and Roger White, Hedden wound up writing his doctoral thesis \u2014 three papers \u2014 on rationality and decision-making. That formed the basis of \u201cReasons without Persons,\u201d whose title alludes to a famous work by philosopher Derek Parfit.<\/p>\n While it might seem unusual to draw to draw a distinction between our past, present, and future selves, Hedden thinks we actually do that frequently, in everyday life and cultural work. In Greek mythology, Odysseus rationally chains himself to the mast of his ship, anticipating that his future self will be irrationally unable to resist the call of the sirens.<\/p>\n \u201cThat\u2019s a dramatic example, but we do this all the time, like when we buy a gym membership and hope that our future selves will irrationally care about sunk costs and go to the gym to avoid having wasted the money,\u201d Hedden says. <\/p>\n Heading down under<\/strong><\/p>\n After earning his MIT PhD, Hedden spent two years as a junior research fellow at Oxford University, then landed his first faculty job in academia \u2014 at the University of Sydney, in Australia, in 2015. Five years later, he moved to Australian National University, in Canberra, leaving when he returned to MIT in 2025. <\/p>\n \u201cI love Australia; I think the quality of life is amazing, the culture is great, the natural world is unbelievable,\u201d Hedden says. The country also has, he observes, \u201ca great philosophy scene,\u201d fed in part by decades of interaction with American scholars. <\/p>\n Hedden\u2019s work kept evolving during his decade in Australia. He started examining specific, applied topics more often, including many questions about legal processes and evidence. For instance: Should juries even deliberate? In one 2017 paper, Hedden suggested they should not, because, among other things, \u201cdeliberation destroys the independence of jurors\u2019 judgments\u201d in ways that can be counterproductive. <\/p>\n Or: Is there such a thing as \u201chigher-order\u201d evidence, which is evidence about what conclusions your evidence supports? In a 2021 paper, Hedden and now-MIT colleague Kevin Dorst concluded that virtually all evidence fits this billing. <\/p>\n Hindsight bias: Not bias<\/strong><\/p>\n Or take another Hedden paper in this vein, from 2019, casting new light on the familiar topic of \u201chindsight bias.\u201d We often alter our views about things after they happen, which can seem like gratuitous second-guessing. <\/p>\n Is it, though? Suppose you are investigating a railroad crash and find evidence that a crash was more likely than people imagined. That might simply be useful new knowledge. Suppose your favorite basketball team loses a game, and you reexamine why you thought they would win; perhaps a star player\u2019s injury was more serious than you imagined. Are you changing your basic views, or just conducting a realistic reassessment?<\/p>\n \u201cThis is perfectly rational and what we should expect,\u201d Hedden says. \u201cSome people say, \u2018Oh, that\u2019s hindsight bias.\u2019 I think it\u2019s just a reasonable conclusion to draw.\u201d<\/p>\n To be sure, in the paper itself, Hedden engages with theoretical philosophical work about evidence and view formation; much of his work bridges academic theory and practical everyday applications. Like many of his papers, this one also evinces the fun of reworking conventional wisdom. <\/p>\n \u201cI do think that these contrarian views are right,\u201d Hedden says. \u201cBut I also find a certain joy in going my own way, or having a skeptical take to get people to rethink views they\u2019re falling into without fully realizing it.\u201d <\/p>\n After an odyssey, back at MIT<\/strong><\/p>\n After nearly a decade in Australia, Hedden received an offer to return to one of his intellectual homes: MIT offered him a place on the faculty. Arriving back at the Institute in 2025, Hedden found many things had changed \u2014 new buildings on campus, new programs \u2014 while some were recognizably the same. <\/p>\n \u201cThe philosophy department looks very similar in terms of the healthy culture,\u201d Hedden says. \u201cIt\u2019s always been known as a collaborative, high-energy place with a fantastic graduate program. And it\u2019s really welcoming. That lounge discussion culture is still there. Sometimes cultures can be fragile. There could have been people who let it lapse. But it\u2019s still there, and that\u2019s great.\u201d<\/p>\n Meanwhile, Hedden has added to his intellectual portfolio by becoming associate dean at SERC, a burgeoning initiative at MIT examining a wide range of civic issues around computing. SERC has supported 40 postdocs around MIT since 2022, in all five MIT schools plus the MIT Schwarzman College of Computing. It has also awarded 30 seed grants for faculty research in the last three years.<\/p>\n \u201cThere\u2019s been really broad interest from faculty and students,\u201d Hedden says. \u201cI\u2019m interacting a lot with computer scientists especially, but people across the Institute everywhere. The College of Computing is a unifying force.\u201d <\/p>\n For that matter, the SERC Scholars program had 75 students accepted last fall, from first-year undergraduates to doctoral candidates, working on projects including surveillance, artificial intelligence, the energy impact of the sector, and more. Hedden is also making a point to develop more courses across SERC topics.<\/p>\n \u201cIt\u2019s often the younger people, undergraduates and graduate students, the postdocs, the junior faculty, that gives us a constant infusion of new ideas and energy,\u201d Hedden says. \u201cWe\u2019re hoping to keep the momentum going.\u201d<\/p>\n In this slice of time, that sounds pretty reasonable. <\/p>\n Source: News Boston \u2013 MIT<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Philosopher Brian Hedden studies decision-making over time \u2014 and recently chose to return to alma mater MIT, where he is now connecting ethics and computing.<\/p>\n","protected":false},"author":1,"featured_media":15238074,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[166],"tags":[],"class_list":["post-15238072","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-boston"],"featured_image_urls":{"full":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb.jpg",1500,1000,false],"thumbnail":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-300x200.jpg",300,200,true],"medium":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-620x413.jpg",620,413,true],"medium_large":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-768x512.jpg",768,512,true],"large":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-940x627.jpg",940,627,true],"1536x1536":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb.jpg",1500,1000,false],"2048x2048":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb.jpg",1500,1000,false],"post-thumbnail":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-998x665.jpg",998,665,true],"ignition_item":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-670x446.jpg",670,446,true],"ignition_item_lg":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-1340x894.jpg",1340,894,true],"ignition_article_media":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-510x510.jpg",510,510,true],"ignition_minicart_item":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-160x160.jpg",160,160,true],"profile_24":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-24x24.jpg",24,24,true],"profile_48":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-48x48.jpg",48,48,true],"profile_96":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-96x96.jpg",96,96,true],"profile_150":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-150x150.jpg",150,150,true],"profile_300":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/08\/15238072-mit-brian-hedden_01-thumb-300x300.jpg",300,300,true]},"author_info":{"display_name":"news.iNthacity","author_link":"https:\/\/www.inthacity.com\/news\/author\/atombo\/"},"category_info":"Boston<\/a>","tag_info":"Boston","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts\/15238072","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/comments?post=15238072"}],"version-history":[{"count":1,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts\/15238072\/revisions"}],"predecessor-version":[{"id":15238073,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts\/15238072\/revisions\/15238073"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/media\/15238074"}],"wp:attachment":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/media?parent=15238072"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/categories?post=15238072"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/tags?post=15238072"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}