Credal sensitivism: threshold vs credence-one JIE GAO, KU LEUVEN NEW TRENDS IN EPISTEMOLOGY, HAMBURG, 05/10/2017
Some background • Clarke, Roger (2013), Belief Is Credence One (In Context), Philosophers’ Imprint • Greco, Daniel (2015), How I Learned to Stop Worrying and Love Probability One, Philosophical Perspective the credence-one view + belief sensitivism (credal sensitivism ) = credence-one sensitivism They argue that credence-one sensitivism is better than the threshold view 1 05/10/17 JIE GAO, KU LEUVEN
The aim of this talk Defend threshold credal sensitivism = the threshold view + credal sensitivism III. Suggest solutions for II. Argue that threshold credal I . Provide evidence for the threshold view sensitivism is better than credal sensitivism credence-one sensitivism 2 05/10/17 JIE GAO, KU LEUVEN
The outline 1. A taxonomy 2. Threshold credal sensitivism vs credence-one sensitivism 3. Defending the threshold 3 05/10/17 JIE GAO, KU LEUVEN
1. A Taxonomy 4 05/10/17 JIE GAO, KU LEUVEN
An overview Sensitivism Non-sensitivism Credal sensitivism Threshold sensitivism The credence-one Credence-one ___ The certainty view view sensitivism The non-credence- Threshold credal The standard threshold Threshold sensitivism one view sensitivism view 5 05/10/17 JIE GAO, KU LEUVEN
Belief sensitivism & non-sensitivism (Non-sensitivism) Belief is context insensitive. The traditional position v (Sensitivism) Belief is context sensitive in the sense that whether one believes that p depends on/is affected by the context Defining contextual factors: - Weatherson (2005), Ganson (2008), Fantl & McGrath (2009), Nagel (2008, 2010): practical factors (interests, stakes, other anxiety-producing factors, etc.) - Clarke (2013, forthcoming): possibilities taken seriously - Greco (2015): live possibilities 6 05/10/17 JIE GAO, KU LEUVEN
Credence-one & certainty (The credence-one view) beliefs require maximal confidence or credence 1. (The certainty view) the credence-one view + non-sensitivism Ø Stability of credence one (In the Bayesian framework, once a rational agent has assigned p probability 1, one’s credence in it can never drop any lower. ) Problems with the certainty view: 1. Counter-intuitiveness : Sometimes people believe things without being certain 2. The betting worry: Dispositions of regarding bets with extremely high stakes to be fair 3. The problem of revision : The agent should not revise any rational belief she has no matter what evidence she receives against. 7 05/10/17 JIE GAO, KU LEUVEN
Non-credence-one + non-sensitivism (The non-credence-one view) Belief does not require maximal confidence or credence 1. • Reductive approach : beliefs are reducible to levels of confidence. (Note: it doesn’t deny the reality of belief) (The threshold view) Beliefs reduce to credences above some threshold (<1). (The standard threshold view) the threshold view + non-sensitivism - Foley (1993, 2009), Hunter (1996), Kaplan (1996), Hawthorne & Bovens (1999), Maher (2006), Eriksson & Hájek (2007) 8 05/10/17 JIE GAO, KU LEUVEN
Problems for the threshold view 1. The lottery problem You own a lottery ticket. You know that there are n tickets in the lottery, that exactly one winner will be selected, that each ticket has an equal chance of winning, and that each ticket’s winning or losing is independent of each other ticket’s winning or losing. For any ticket i , let L i be the proposition that i loses; then for all i, you have Cr(L i ) = !"# ! . On the standard threshold view, if n is sufficiently high, it is impossible for you not to believe that your ticket will lose, which is strikingly counterintuitive. 9 05/10/17 JIE GAO, KU LEUVEN
Problems for the threshold view 2. The arbitrariness problem As Robert Stalnaker (1984: 91) emphasised, any number r [the threshold] is bound to seem arbitrary. Unless these numbers are made salient by the environment, there is no special difference between believing p to degree 0.9786 and believing it to degree 0.9875. But if r is 0.98755, this will be the difference between believing p and not believing it, which is an important difference. (Weatherson 2005: 420) There doesn't seem to be a non-arbitrary way of identifying a threshold, even a vague one. 10 05/10/17 JIE GAO, KU LEUVEN
Problems for the threshold view 3. The problem with qualitative commitments involved in beliefs i. Behavioural dispositions : Believing p involves simply take p for granted, but a change of credence within a certain interval doesn’t necessarily create a qualitative difference to one’s dispositions. ii. Truth commitment : Beliefs involve a commitment to the truth of their content, but having credence in p just meeting a threshold less than 1 implies assigning a positive credence to the negation of p . - Fantl and McGrath (2009), Ross and Schroeder (2014) • How is it that changes of credence that just falls short of the threshold do not make any qualitative difference, while changes passing the threshold make big differences in one’s dispositions? 11 05/10/17 JIE GAO, KU LEUVEN
Reconsidering credence-one The credence-one view can easily solve problems for the threshold view: - (Clarke 2013, Greco 2015) 1) The lottery problem ü There is no lottery large enough to make !"# ! = 1. 2) The arbitrariness problem ü Believing p to degree 1. 3) The problem with qualitative commitments involved in beliefs ü If one believes p to degree 1, she will not engage in any activities of taking not- p into consideration. 12 05/10/17 JIE GAO, KU LEUVEN
Credence-one sensitivism Sensitivism solves standard problems for the credence-one view: 1. Counter-intuitiveness ü Belief to degree 1 should not be taken to entail certainty. Certainty requires a stability of opinion across contexts that credence one does not have. 2. The betting worry ü Offering a bet means changing the context. When the practical importance of p changes, as it must when a bet is offered, the space of salient alternatives to p may also change. 3. The problem of revision ü New counter evidence changes the space of alternative possibilities and hence induce changes to the context. 13 05/10/17 JIE GAO, KU LEUVEN
Motivating sensitivism 1. Belief’s sensitivity to practical factors i. Functional properties of belief: Ganson (2008): in order to count as believing p in a range of circumstances, one must be willing to act as if p in those circumstances. (see also Weatherson 2005, Fantl & McGrath 2009) ii. Psychological features of belief: Nagel (2008, 2010)’s analyses of belief regulation of normal human beings in different practical settings support sensitivism. 2. Belief and assertion S ’s assertion that p is sincere iff S believes that p . S’s sincere assertion takes place against a common ground. Common ground can be modeled as a set of possibilities taken seriously for the purposes of the conversation. (Clarke forthcoming, Greco 2015) 14 05/10/17 JIE GAO, KU LEUVEN
Sensitivism Non-sensitivism Credal sensitivism Threshold sensitivism The credence-one Credence-one ___ The certainty view view sensitivism The non-credence- Threshold credal The standard threshold Threshold sensitivism one view sensitivism view 15 05/10/17 JIE GAO, KU LEUVEN
Credal vs threshold sensitivism (Threshold sensitivism) Credence is context insensitive; the threshold on credence necessary for belief varies in accordance with relevant contextual factors; the contextual sensitivity of the threshold explains the contextual sensitivity of belief. - Weatherson (2005), Ganson (2008), Fantl & McGrath (2009), Bach (2005, 2008) endorse a version of threshold sensitivism (threshold pragmatism). But they simply stipulate it without neither argument nor evidence. (Credal sensitivism) Credence is context sensitive; the contextual sensitivity of credence explains the contextual sensitivity of belief. - Can be combined with either the credence-one view or the threshold view 16 05/10/17 JIE GAO, KU LEUVEN
Motivating credal sensitivism Credal sensitivism is entailed by credence-one sensitivism: One’s credences in a particular context are given by a function assigning weights to each of the salient possibilities in that context. When salient possibilities become more or fewer, one’s credences are given by a different function. This implies that credence distributions vary contextually. 17 05/10/17 JIE GAO, KU LEUVEN
Motivating credal sensitivism Independent evidence: 1. Psychological filters of error possibilities When we’re deliberating, a largely unconscious, automatic decision set-up process filters out certain possibilities we treat as live from a highly complex range of possibilities, and then credences will be assigned to those possibilities “on the spot”. Which possibilities get through the filter is a highly context-sensitive matter. (Norby 2015) 18 05/10/17 JIE GAO, KU LEUVEN
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