I defend the following version of the ought-implies-can principle: (OIC) by virtue of conceptual ... more I defend the following version of the ought-implies-can principle: (OIC) by virtue of conceptual necessity, an agent at a given time has an (objective, pro tanto) obligation to do only what the agent at that time has the ability and opportunity to do. In short, obligations correspond to ability plus opportunity. My argument has three premises: (1) obligations correspond to reasons for action; (2) reasons for action correspond to potential actions; (3) potential actions correspond to ability plus opportunity. In the bulk of the paper I address six objections to OIC: three objections based on putative counterexamples, and three objections based on arguments to the effect that OIC conflicts with the is/ought thesis, the possibility of hard determinism, and the denial of the Principle of Alternate Possibilities.
The first sentence of NE I.2 has roughly the form: "If A [there is a universal end] and B (becaus... more The first sentence of NE I.2 has roughly the form: "If A [there is a universal end] and B (because, if not-B, then C), then D [this end will be the best good]". According to some commentators, Aristotle uses B to infer A; but then the sentence is fallacious. According to other commentators, Aristotle does not use B (until later on); but then the sentence is bizarre. Contrary to both sets of commentators (but following Wedin 1981), I suggest that Aristotle uses B together with A to infer validly that there is a non-instrumentaland thus uniqueuniversal end (hence D). On this interpretation the above two problems disappear, but a subtler problem emerges: not-B does not entail C.
1980) proposed the Principal Principle (PP) and a "reformulation" which later on he called 'OP' (... more 1980) proposed the Principal Principle (PP) and a "reformulation" which later on he called 'OP' (Old Principle). Reacting to his belief that these principles run into trouble, Lewis (1994) concluded that they should be replaced with the New Principle (NP). This conclusion left Lewis uneasy, because he thought that an inverse form of NP is "quite messy", whereas an inverse form of OP, namely the simple and intuitive PP, is "the key to our concept of chance". I argue that, even if OP should be discarded, FP need not be. Moreover, far from being messy, an inverse form of NP is a simple and intuitive Conditional Principle (CP). Finally, both PP and CP are special cases of a General Principle (GP); it follows that so are PP and NP, which are thus compatible rather than competing.
According to Hempel's paradox, evidence (E) that an object is a nonblack nonraven confirms the hy... more According to Hempel's paradox, evidence (E) that an object is a nonblack nonraven confirms the hypothesis (H) that every raven is black. According to the standard Bayesian solution, E does confirm H but only to a minute degree. This solution relies on the almost never explicitly defended assumption that the probability of H should not be affected by evidence that an object is nonblack. I argue that this assumption is implausible, and I propose a way out for Bayesians.
Kadri Vihvelin, in ''What time travelers cannot do'' (Philos Stud 81:315-330, 1996), argued that ... more Kadri Vihvelin, in ''What time travelers cannot do'' (Philos Stud 81:315-330, 1996), argued that ''no time traveler can kill the baby who in fact is her younger self'', because (V1) ''if someone would fail to do something, no matter how hard or how many times she tried, then she cannot do it'', and if a time traveler tried to kill her baby self, she would always fail. Theodore Sider (Philos Stud 110:115-138, 2002) criticized Vihvelin's argument, and Ira Kiourti (Philos Stud 139:343-352, 2008) criticized both Vihvelin's argument and Sider's critique. I present a critique of Vihvelin's argument different from both Sider's and Kiourti's critiques: I argue in a novel way that both V1 and V2 are false. Since Vihvelin's argument might be understood as providing a challenge to the possibility of time travel, if my critique succeeds then time travel survives such a challenge unscathed.
Imperatives cannot be true or false, so they are shunned by logicians. And yet imperatives can be... more Imperatives cannot be true or false, so they are shunned by logicians. And yet imperatives can be combined by logical connectives: "kiss me and hug me" is the conjunction of "kiss me" with "hug me". This example may suggest that declarative and imperative logic are isomorphic: just as the conjunction of two declaratives is true exactly if both conjuncts are true, the conjunction of two imperatives is satisfied exactly if both conjuncts are satisfied-what more is there to say? Much more, I argue. "If you love me, kiss me", a conditional imperative, mixes a declarative antecedent ("you love me") with an imperative consequent ("kiss me"); it is satisfied if you love and kiss me, violated if you love but don't kiss me, and avoided if you don't love me. So we need a logic of three-valued imperatives which mixes declaratives with imperatives. I develop such a logic.
Surrender; therefore, surrender or fight" is apparently an argument corresponding to an inference... more Surrender; therefore, surrender or fight" is apparently an argument corresponding to an inference from an imperative to an imperative.
Suppose that a sign at the entrance of a restaurant reads: "Do not enter these premises unless yo... more Suppose that a sign at the entrance of a restaurant reads: "Do not enter these premises unless you have a reservation and you are properly attired. " You see someone who is properly attired and is about to enter, and you tell her: "Don't enter these premises if you don't have a reservation. " She asks why, and you reply: "It follows from what the sign says. " It seems that you made a valid inference from an imperative premise to an imperative conclusion. But it also seems that imperatives cannot be true or false; so in what sense is your inference valid? Its validity cannot consist in the truth of its premise guaranteeing the truth of its conclusion. One is thus faced with "Jørgensen's dilemma" (Ross 1941: 55-6): apparently, imperative logic cannot exist, because logic deals only with entities that, unlike imperatives, can be true or false; but apparently, imperative logic must exist. It must exist not only because inferences with imperatives can be valid, but also because imperatives (like "Enter" and "Don't enter") can be inconsistent with each other, and because one can apply logical operations to imperatives: "Don't enter" is the negation of "Enter, " and "Sing or dance" is the disjunction of "Sing" and "Dance. " A standard reaction to this dilemma consists in basing imperative logic on analogues of truth and falsity. For example, the imperative "Don't enter" is satisfied if you don't enter and is violated if you enter, and one might say that an inference from an imperative premise to an imperative conclusion is valid exactly if the satisfaction (rather than the truth) of the premise guarantees the satisfaction of the conclusion. Imperative logic may matter for metaethics (SEE METAETHICS): if one understands moral claims as disguised imperatives (see PRESCRIPTIVISM) and thus as lacking truth values (see NON-COGNITIVISM), then imperative logic may help explain how inferences involving moral claims can be valid (see FREGE-GEACH OBJECTION). But before getting into the details of imperative logic, more needs to be said about what exactly imperatives are.
You may not know me well enough to evaluate me in terms of my moral character, but I take it you ... more You may not know me well enough to evaluate me in terms of my moral character, but I take it you believe I can be evaluated: it sounds strange to say that I am indeterminate, neither good nor bad nor intermediate. Yet I argue that the claim that most people are indeterminate is the conclusion of a sound argument-the indeterminacy paradox-with two premises: (1) most people are fragmented (they would behave deplorably in many and admirably in many other situations); (2) fragmentation entails indeterminacy. I support (1) by examining psychological experiments in which most participants behave deplorably (e.g., by maltreating ''prisoners'' in a simulated prison) or admirably (e.g., by intervening in a simulated theft). I support (2) by arguing that, according to certain plausible conceptions, character evaluations presuppose behavioral consistency (lack of fragmentation). Possible reactions to the paradox include: (a) denying that the experiments are relevant to character; (b) upholding conceptions according to which character evaluations do not presuppose consistency; (c) granting that most people are indeterminate and explaining why it appears otherwise. I defend (c) against (a) and (b).
Besides pure declarative arguments, whose premises and conclusions are declaratives ("you sinned ... more Besides pure declarative arguments, whose premises and conclusions are declaratives ("you sinned shamelessly; so you sinned"), and pure imperative arguments, whose premises and conclusions are imperatives ("repent quickly; so repent"), there are mixed-premise arguments, whose premises include both imperatives and declaratives ("if you sinned, repent; you sinned; so repent"), and cross-species arguments, whose premises are declaratives and whose conclusions are imperatives ("you must repent; so repent") or vice versa ("repent; so you can repent"). I propose a general definition of argument validity: an argument is valid exactly if, necessarily, every fact that sustains its premises also sustains its conclusion, where a fact sustains an imperative exactly if it favors the satisfaction over the violation proposition of the imperative, and a fact sustains a declarative exactly if, necessarily, the declarative is true if the fact exists. I argue that this definition yields as special cases the standard definition of validity for pure declarative arguments and my previously defended definition of validity for pure imperative arguments, and that it yields intuitively acceptable results for mixed-premise and cross-species arguments.
If (backward) time travel is possible, presumably so is my shooting my younger self (YS); then ap... more If (backward) time travel is possible, presumably so is my shooting my younger self (YS); then apparently I can kill him -I can commit retrosuicide. But if I were to kill him I would not exist to shoot him, so how can I kill him? The standard solution to this paradox understands ability as compossibility with the relevant facts and points to an equivocation about which facts are relevant: my killing YS is compossible with his proximity but not with his survival, so I can kill him if facts like his survival are irrelevant but I cannot if they are relevant. I identify a lacuna in this solution, namely its reliance without argument on the hidden assumption that my killing YS is possible: if it is impossible, it is not compossible with anything. I argue that this lacuna is important, and I sketch a different solution to the paradox.
I defend the epistemic thesis that evaluations of people in terms of their moral character as goo... more I defend the epistemic thesis that evaluations of people in terms of their moral character as good, bad, or intermediate are almost always epistemically unjustified. (1) Because most people are fragmented (they would behave deplorably in many and admirably in many other situations), one's prior probability that any given person is fragmented should be high.
Pretheoretically, (B) 'all believers are immortal' is about all believers, but (1) B is not about... more Pretheoretically, (B) 'all believers are immortal' is about all believers, but (1) B is not about any unbeliever. Similarly, (M) 'all mortals are unbelievers' is not about any immortal, but (2) M is about all mortals. But B and M are logically equivalent universal generalizations, so arguably they are about exactly the same objects; by , they are about those mortals who are unbelievers, contradicting (1). If one responds by giving up , is there still a sense in which B treats unbelievers differently from believers? I argue that there is. B is uninformative about unbelievers but informative about believers, in the following sense: for any object o, the information that B provides only about o-namely, 'o is a believer only if o is immortal'-is entailed (and thus rendered redundant) by 'o is an unbeliever' but not by 'o is a believer'.
The Principal Principle (PP) says that, for any proposition A, given any admissible evidence and ... more The Principal Principle (PP) says that, for any proposition A, given any admissible evidence and the proposition that the chance of A is x%, one's conditional credence in A should be x%. Humean Supervenience (HS) claims that, among possible worlds like ours, no two differ without differing in the spacetime-point-by-spacetimepoint arrangement of local properties. David has argued that PP contradicts HS, and the validity of his argument has been endorsed by Bigelow et al.
I defend the following version of the ought-implies-can principle: (OIC) by virtue of conceptual ... more I defend the following version of the ought-implies-can principle: (OIC) by virtue of conceptual necessity, an agent at a given time has an (objective, pro tanto) obligation to do only what the agent at that time has the ability and opportunity to do. In short, obligations correspond to ability plus opportunity. My argument has three premises: (1) obligations correspond to reasons for action; (2) reasons for action correspond to potential actions; (3) potential actions correspond to ability plus opportunity. In the bulk of the paper I address six objections to OIC: three objections based on putative counterexamples, and three objections based on arguments to the effect that OIC conflicts with the is/ought thesis, the possibility of hard determinism, and the denial of the Principle of Alternate Possibilities.
The first sentence of NE I.2 has roughly the form: "If A [there is a universal end] and B (becaus... more The first sentence of NE I.2 has roughly the form: "If A [there is a universal end] and B (because, if not-B, then C), then D [this end will be the best good]". According to some commentators, Aristotle uses B to infer A; but then the sentence is fallacious. According to other commentators, Aristotle does not use B (until later on); but then the sentence is bizarre. Contrary to both sets of commentators (but following Wedin 1981), I suggest that Aristotle uses B together with A to infer validly that there is a non-instrumentaland thus uniqueuniversal end (hence D). On this interpretation the above two problems disappear, but a subtler problem emerges: not-B does not entail C.
1980) proposed the Principal Principle (PP) and a "reformulation" which later on he called 'OP' (... more 1980) proposed the Principal Principle (PP) and a "reformulation" which later on he called 'OP' (Old Principle). Reacting to his belief that these principles run into trouble, Lewis (1994) concluded that they should be replaced with the New Principle (NP). This conclusion left Lewis uneasy, because he thought that an inverse form of NP is "quite messy", whereas an inverse form of OP, namely the simple and intuitive PP, is "the key to our concept of chance". I argue that, even if OP should be discarded, FP need not be. Moreover, far from being messy, an inverse form of NP is a simple and intuitive Conditional Principle (CP). Finally, both PP and CP are special cases of a General Principle (GP); it follows that so are PP and NP, which are thus compatible rather than competing.
According to Hempel's paradox, evidence (E) that an object is a nonblack nonraven confirms the hy... more According to Hempel's paradox, evidence (E) that an object is a nonblack nonraven confirms the hypothesis (H) that every raven is black. According to the standard Bayesian solution, E does confirm H but only to a minute degree. This solution relies on the almost never explicitly defended assumption that the probability of H should not be affected by evidence that an object is nonblack. I argue that this assumption is implausible, and I propose a way out for Bayesians.
Kadri Vihvelin, in ''What time travelers cannot do'' (Philos Stud 81:315-330, 1996), argued that ... more Kadri Vihvelin, in ''What time travelers cannot do'' (Philos Stud 81:315-330, 1996), argued that ''no time traveler can kill the baby who in fact is her younger self'', because (V1) ''if someone would fail to do something, no matter how hard or how many times she tried, then she cannot do it'', and if a time traveler tried to kill her baby self, she would always fail. Theodore Sider (Philos Stud 110:115-138, 2002) criticized Vihvelin's argument, and Ira Kiourti (Philos Stud 139:343-352, 2008) criticized both Vihvelin's argument and Sider's critique. I present a critique of Vihvelin's argument different from both Sider's and Kiourti's critiques: I argue in a novel way that both V1 and V2 are false. Since Vihvelin's argument might be understood as providing a challenge to the possibility of time travel, if my critique succeeds then time travel survives such a challenge unscathed.
Imperatives cannot be true or false, so they are shunned by logicians. And yet imperatives can be... more Imperatives cannot be true or false, so they are shunned by logicians. And yet imperatives can be combined by logical connectives: "kiss me and hug me" is the conjunction of "kiss me" with "hug me". This example may suggest that declarative and imperative logic are isomorphic: just as the conjunction of two declaratives is true exactly if both conjuncts are true, the conjunction of two imperatives is satisfied exactly if both conjuncts are satisfied-what more is there to say? Much more, I argue. "If you love me, kiss me", a conditional imperative, mixes a declarative antecedent ("you love me") with an imperative consequent ("kiss me"); it is satisfied if you love and kiss me, violated if you love but don't kiss me, and avoided if you don't love me. So we need a logic of three-valued imperatives which mixes declaratives with imperatives. I develop such a logic.
Surrender; therefore, surrender or fight" is apparently an argument corresponding to an inference... more Surrender; therefore, surrender or fight" is apparently an argument corresponding to an inference from an imperative to an imperative.
Suppose that a sign at the entrance of a restaurant reads: "Do not enter these premises unless yo... more Suppose that a sign at the entrance of a restaurant reads: "Do not enter these premises unless you have a reservation and you are properly attired. " You see someone who is properly attired and is about to enter, and you tell her: "Don't enter these premises if you don't have a reservation. " She asks why, and you reply: "It follows from what the sign says. " It seems that you made a valid inference from an imperative premise to an imperative conclusion. But it also seems that imperatives cannot be true or false; so in what sense is your inference valid? Its validity cannot consist in the truth of its premise guaranteeing the truth of its conclusion. One is thus faced with "Jørgensen's dilemma" (Ross 1941: 55-6): apparently, imperative logic cannot exist, because logic deals only with entities that, unlike imperatives, can be true or false; but apparently, imperative logic must exist. It must exist not only because inferences with imperatives can be valid, but also because imperatives (like "Enter" and "Don't enter") can be inconsistent with each other, and because one can apply logical operations to imperatives: "Don't enter" is the negation of "Enter, " and "Sing or dance" is the disjunction of "Sing" and "Dance. " A standard reaction to this dilemma consists in basing imperative logic on analogues of truth and falsity. For example, the imperative "Don't enter" is satisfied if you don't enter and is violated if you enter, and one might say that an inference from an imperative premise to an imperative conclusion is valid exactly if the satisfaction (rather than the truth) of the premise guarantees the satisfaction of the conclusion. Imperative logic may matter for metaethics (SEE METAETHICS): if one understands moral claims as disguised imperatives (see PRESCRIPTIVISM) and thus as lacking truth values (see NON-COGNITIVISM), then imperative logic may help explain how inferences involving moral claims can be valid (see FREGE-GEACH OBJECTION). But before getting into the details of imperative logic, more needs to be said about what exactly imperatives are.
You may not know me well enough to evaluate me in terms of my moral character, but I take it you ... more You may not know me well enough to evaluate me in terms of my moral character, but I take it you believe I can be evaluated: it sounds strange to say that I am indeterminate, neither good nor bad nor intermediate. Yet I argue that the claim that most people are indeterminate is the conclusion of a sound argument-the indeterminacy paradox-with two premises: (1) most people are fragmented (they would behave deplorably in many and admirably in many other situations); (2) fragmentation entails indeterminacy. I support (1) by examining psychological experiments in which most participants behave deplorably (e.g., by maltreating ''prisoners'' in a simulated prison) or admirably (e.g., by intervening in a simulated theft). I support (2) by arguing that, according to certain plausible conceptions, character evaluations presuppose behavioral consistency (lack of fragmentation). Possible reactions to the paradox include: (a) denying that the experiments are relevant to character; (b) upholding conceptions according to which character evaluations do not presuppose consistency; (c) granting that most people are indeterminate and explaining why it appears otherwise. I defend (c) against (a) and (b).
Besides pure declarative arguments, whose premises and conclusions are declaratives ("you sinned ... more Besides pure declarative arguments, whose premises and conclusions are declaratives ("you sinned shamelessly; so you sinned"), and pure imperative arguments, whose premises and conclusions are imperatives ("repent quickly; so repent"), there are mixed-premise arguments, whose premises include both imperatives and declaratives ("if you sinned, repent; you sinned; so repent"), and cross-species arguments, whose premises are declaratives and whose conclusions are imperatives ("you must repent; so repent") or vice versa ("repent; so you can repent"). I propose a general definition of argument validity: an argument is valid exactly if, necessarily, every fact that sustains its premises also sustains its conclusion, where a fact sustains an imperative exactly if it favors the satisfaction over the violation proposition of the imperative, and a fact sustains a declarative exactly if, necessarily, the declarative is true if the fact exists. I argue that this definition yields as special cases the standard definition of validity for pure declarative arguments and my previously defended definition of validity for pure imperative arguments, and that it yields intuitively acceptable results for mixed-premise and cross-species arguments.
If (backward) time travel is possible, presumably so is my shooting my younger self (YS); then ap... more If (backward) time travel is possible, presumably so is my shooting my younger self (YS); then apparently I can kill him -I can commit retrosuicide. But if I were to kill him I would not exist to shoot him, so how can I kill him? The standard solution to this paradox understands ability as compossibility with the relevant facts and points to an equivocation about which facts are relevant: my killing YS is compossible with his proximity but not with his survival, so I can kill him if facts like his survival are irrelevant but I cannot if they are relevant. I identify a lacuna in this solution, namely its reliance without argument on the hidden assumption that my killing YS is possible: if it is impossible, it is not compossible with anything. I argue that this lacuna is important, and I sketch a different solution to the paradox.
I defend the epistemic thesis that evaluations of people in terms of their moral character as goo... more I defend the epistemic thesis that evaluations of people in terms of their moral character as good, bad, or intermediate are almost always epistemically unjustified. (1) Because most people are fragmented (they would behave deplorably in many and admirably in many other situations), one's prior probability that any given person is fragmented should be high.
Pretheoretically, (B) 'all believers are immortal' is about all believers, but (1) B is not about... more Pretheoretically, (B) 'all believers are immortal' is about all believers, but (1) B is not about any unbeliever. Similarly, (M) 'all mortals are unbelievers' is not about any immortal, but (2) M is about all mortals. But B and M are logically equivalent universal generalizations, so arguably they are about exactly the same objects; by , they are about those mortals who are unbelievers, contradicting (1). If one responds by giving up , is there still a sense in which B treats unbelievers differently from believers? I argue that there is. B is uninformative about unbelievers but informative about believers, in the following sense: for any object o, the information that B provides only about o-namely, 'o is a believer only if o is immortal'-is entailed (and thus rendered redundant) by 'o is an unbeliever' but not by 'o is a believer'.
The Principal Principle (PP) says that, for any proposition A, given any admissible evidence and ... more The Principal Principle (PP) says that, for any proposition A, given any admissible evidence and the proposition that the chance of A is x%, one's conditional credence in A should be x%. Humean Supervenience (HS) claims that, among possible worlds like ours, no two differ without differing in the spacetime-point-by-spacetimepoint arrangement of local properties. David has argued that PP contradicts HS, and the validity of his argument has been endorsed by Bigelow et al.
Uploads
Papers by Peter Vranas