Alexander R. Pruss

Some, notably Peter van Inwagen, in order to avoid problems with free will and omniscience, replace the condition that an omniscient being knows all true propositions with a version of the apparently weaker condition that an omniscient being knows all knowable true propositions. I shall show that the apparently weaker condition, when conjoined with uncontroversial claims and the logical closure of an omniscient being's knowledge, still yields the claim that an omniscient being knows all true propositions.

This thesis examines the alethic modal concepts of possibility and necessity. It is argued that one cannot do justice to all our modal talk without possible worlds, i.e., complete ways that a cosmos might have been. I argue that not all of the proposed applications of possible worlds succeed but enough remain to give one good theoretical reason to posit them. The two central problems now are: What feature of reality makes correct alethic modal claims true and What are possible worlds? ;David Lewis makes possible worlds be concretely existing universes. Unfortunately, I show Lewis's account involves set-theoretic, ethical, inductive and probabilistic paradoxes, and commits Lewis to an objectionable form of primitive modality that governs the choice of the counterpart relation. The most promising contemporary alternatives to Lewis's theory have been the worlds of Adams and Plantinga constructed out of Platonic entities such as maximal collections of consistent propositions. However, these approaches fail to provide a satisfactory answer to the question of what makes true modal claims true. I also criticize some alternative accounts. ;Finally, I discuss and combine two historical approaches. The first is an Aristotelian approach that says a non-actual event is possible is to say that some actual substances could have initiated a causal chain that could lead up to the event in question. However, it can be shown that some plausible global possibility claims can be made true on this account only if there is a necessarily existent first cause capable of initiating very different universes. On the other hand, Leibniz made possible worlds be ideas in the mind of an omniscient necessarily existent deity. Leibniz fails to explain what it is that makes these possible worlds possible, but if we were willing to combine his story with the conclusion drawn from the Aristotelian one, we could get the following story: Possible worlds are ideas in the mind of an omniscient deity and what makes them possible is that this deity has the Aristotelian capability of initiating causal chains that can lead to them being actualized

Popper functions allow one to take conditional probabilities as primitive instead of deriving them from unconditional probabilities via the ratio formula P=P/P. A major advantage of this approach is it allows one to condition on events of zero probability. I will show that under plausible symmetry conditions, Popper functions often fail to do what they were supposed to do. For instance, suppose we want to define the Popper function for an isometrically invariant case in two dimensions and hence require the Popper function to be rotationally invariant and defined on pairs of sets from some algebra that contains at least all countable subsets. Then it turns out that the Popper function trivializes for all finite sets: P=1 for all A ) if B is finite. Likewise, Popper functions invariant under all sequence reflections can’t be defined in a way that models a bidirectionally infinite sequence of independent coin tosses

The cosmological and teleological argument both start with some contingent feature of the actual world and argue that the best or only explanation of that feature is that it was produced by an intelligent and powerful supernatural being. The cosmological argument starts with a general feature, such as the existence of contingent being or the presence of motion and uses some version of the Principle of Sufficient Reason to conclude that this feature must have an explanation. The debate then focuses on two points: first, whether the PSR in question is true, and second, whether the explanation must involve God or at least some God-like being. The teleological argument begins with a general feature of the cosmos judged to have value, such as the existence of intelligent life or the presence of order in the universe, and argues, usually inductively but sometimes deductively, that this feature is to be explained by the agency of a powerful supernatural being. Here, the debate tends to focus on whether there are alternate naturalistic explanations, such as Darwinian evolution.

Adhering to the traditional concept of omniscience lands Gale in the incoherence Grim’s Cantorian arguments reveal in talk of “all propositions.” By constructing variants and extensions of Grim’s arguments, I explain why various ways out of the incoherence are unacceptable, why theists would do better to adopt a certain revisionary concept of omniscience, and why the Cantorian troubles are so deep as to be troubles as well for Gale’s Weak PSR. I conclude with some brief reflections on method, suggesting that we pursue the full implications of Gale’s own revisionary remarks and replace his method of analytic argumentation with non-analytic revisionary theory-construction.

Consider the regularity thesis that each possible event has non-zero probability. Hájek challenges this in two ways: there can be nonmeasurable events that have no probability at all and on a large enough sample space, some probabilities will have to be zero. But arguments for the existence of nonmeasurable events depend on the axiom of choice. We shall show that the existence of anything like regular probabilities is by itself enough to imply a weak version of AC sufficient to prove the Banach–Tarski Paradox on the decomposition of a ball into two equally sized balls, and hence to show the existence of nonmeasurable events. This provides a powerful argument against unrestricted orthodox Bayesianism that works even without AC. A corollary of our formal result is that if every partial order extends to a total preorder while maintaining strict comparisons, then the Banach–Tarski Paradox holds. This yields an argument that incommensurability cannot be avoided in ambitious versions of decision theory

Plural quantification, often used to evade Russell paradoxes, will lead back to them, given certain assumptions about propositions. This chapter provides a more generalized version of the path to paradox by showing that any theory that makes possible the construction of an appropriate packaging relation falls prey to a Russell paradox. It gives examples of widely-held metaphysical theories that require such a relation. It shows that the paradoxes that can result from plural quantification are more widely damaging, and harder to tame, than has been recognized. It also displays formal requirements that any metaphysical framework with a packaging relation must meet if it is to have a chance of escaping self-contradiction. The chapter first gives the general paradox-generating setup, and then shows how three families of metaphysical assumptions allow one to instantiate it. It concludes by assessing the aftermath of the arguments presented.

The Adams Thesis holds for a conditional → and a probability assignment P if and only if P=P whenever P>0. The restriction ensures that P is well defined by the classical formula P=P/P. Drawing on deep results of Maharam on measure algebras, it is shown that, notwithstanding well-known triviality results, any probability space can be extended to a probability space with a new conditional satisfying the Adams Thesis and satisfying a number of axioms for conditionals. This puts significant limits on how far triviality results can go.

There is a basic dividing line in the philosophy of time. According to the B-theory, we can describe the temporal reality of the world with freely repeatable sentences, using designators of fixed times and relations such as "earlier" and "later." The A-theory contends that there is an ontological feature of the world which is described by explicitly tensed statements such as "I am now writing this review," and which is not captured by any B-theoretic statements such as "I write this review at t1," whereas the B-theory will say that ontologically there is nothing to my writing this review now but my writing this review at t1. Since most present-day B-theorists will grant that propositions formulated in A-theoretic terms cannot in general be translated into propositions formulated in B-theoretic terms, the debate is over ontology, not translation. In his accessible, interesting, provocative, and at times quite insightful book, David Cockburn argues that the debate cannot be resolved by the kind of ontological and linguistic analysis that is most commonly brought to bear upon the issue by analytic philosophy. Instead, the debate should be moved to a more anthropocentric field, and based upon the significance of time for our concerns, desires, feelings, and actions: "[the] fundamental issues in the philosophy of time... can only be properly grasped within a framework in which the significance of time in our ethical thinking has a central place". This bold claim forming the centrepiece of Cockburn's book will of course set off alarm bells for philosophers of a scientistic persuasion for whom "anthropocentric" is an insult term, and whose dearest desire is to move to a point of view that abstracts from human feelings and concerns.

The latter third of the 20th century has seen the philosophical defence of theism - many philosophers were caught off-guard because they assumed that metaphysics and theology had been dealt with. Moreover, the leaders of this renaissance were analytically-rooted philosophers. Upon examination however, it is clear that significant developments in philosophical theism historically have come upon the heels of breakthroughs in the core areas of philosophy concerning meaning, logic and scientific methodology - cornerstones of analytic philosophy. This volume attempts to document this golden era of analytical theism.

Classical real-valued probabilities come at a philosophical cost: in many infinite situations, they assign the same probability value—namely, zero—to cases that are impossible as well as to cases that are possible. There are three non-classical approaches to probability that can avoid this drawback: full conditional probabilities, qualitative probabilities and hyperreal probabilities. These approaches have been criticized for failing to preserve intuitive symmetries that can be preserved by the classical probability framework, but there has not been a systematic study of the conditions under which these symmetries can and cannot be preserved. This paper fills that gap by giving complete characterizations under which symmetries understood in a certain “strong” way can be preserved by these non-classical probabilities, as well as by offering some results to make it plausible that the strong notion of symmetry here is the right one. Philosophical implications are briefly discussed, but the main purpose of the paper is to offer technical results to help make further philosophical discussion more sophisticated.

SpinozaÂ’s God is a being with infinite attributes, each of which expresses infinite essence. Does this mean that God has infinitely many attributes, each of which expresses infinite essence, or does God simply have attributes, each of which is infinite and expresses infinite essence? SpinozaÂ’s argumentation in Letter 9 and the Scholium to Prop. I.10 clearly indicates that it is not just each individual attribute that is infinite, but there are in some sense infinitely many of them. This would seem to settle the issue, except that Spinoza never talks of more than two attributes, Extension..

I shall discuss the problem of the definition of lying and the formulation of the duty of truthtelling. I shall argue that the morality of assertion is a special case of the morality of endorsement, and that a criterion of adequacy for an account of lying is that it handles certain cases of dishonest endorsement as well. Standardviews of lying fail to do so. I shall offer an account of the duty of honest endorsement in terms of the intention to avoid falsehood. But, in the end, we may simplyhave reason to go back to the naïve view that lying is saying falsehoods.

It is often loosely said that Ramsey The foundations of mathematics and other logical essays, Routledge and Kegan Paul, Abingdon, pp 156–198, 1931) and de Finetti Studies in subjective probability, Kreiger Publishing, Huntington, 1937) proved that if your credences are inconsistent, then you will be willing to accept a Dutch Book, a wager portfolio that is sure to result in a loss. Of course, their theorems are true, but the claim about acceptance of Dutch Books assumes a particular method of calculating expected utilities given the inconsistent credences. I will argue that there are better ways of calculating expected utilities given a potentially inconsistent credence assignment, and that for a large class of credences—a class that includes many inconsistent examples—these ways are immune to Dutch Books and single-shot domination failures. The crucial move is to replace Finite Additivity with Monotonicity, then \\le P\)) and then calculate expected utilities for positive U via the formula \\, dy\). This shows that Dutch Book arguments for probabilism, the thesis that one’s credences should be consistent, do not establish their conclusion. Finally, I will consider a modified argument based on multi-step domination failure that does better, but nonetheless is not as compelling as the Dutch Book arguments appeared to be.

In simplified form, the argument that I am defending holds that the incompatibility of our freedom with determinism follows from the conjunction of (1) a plausible supervenience claim which says that whether a human agent is free depends only on what happens during the agent’s life and (2) a freedom-cancellation principle of Richard Gale which says that an agent is not free if all of her actions are intentionally brought about by another agent. Improved versions of (1) and (2) are also considered

The free-will defence holds that the value of significant free will is so great that God is justified in creating significantly free creatures even if there is a risk or certainty that these creatures will sin. A difficulty for the FWD, developed carefully by Quentin Smith, is that God is unable to do evil, and yet surely lacks no genuinely valuable kind of freedom. Smith argues that the kind of freedom that God has can be had by creatures, without a risk of creatures doing evil. I shall show that Smith's argument fails – the case of God is disanalogous to the case of creatures precisely because creatures are creatures