Is the fact that other people believe in God a reason to believe? Remarks on the consensus gentium argument.

According to The Consensus Gentium Argument from the premise: “Everyone believes that God exists” one can conclude that God does exist. In my paper I analyze two ways of defending the claim that somebody’s belief in God is a prima facie reason to believe. Kelly takes the fact of the commonness of the belief in God as a datum to explain and argues that the best explanation has to indicate the truthfulness of the theistic belief. Trinkaus Zagzebski grounds her defence on rationality of epistemic trust in others. In the paper I argue that the second line of reasoning is more promising and I propose its improved version.

Gestation and Parental Rights: Why is Good Enough Good Enough?

In this paper I explore the question of whether gestation can ground parental rights. I consider Anca Gheaus’s (2012) claim that the labour and bonding of gestation give one the right to parent one’s biological child. I argue that, while Gheaus’s gestational account of parental rights is the most successful of such accounts in the literature, it is ultimately unsuccessful, because the concept ‘maternal-fetal bonding’ does not stand up to scrutiny. Gheaus argues that the labour expended in gestation generates parental rights. This is a standard, Lockean sort of a move in parental ethics—it usually relies on the claim that I have proprietary rights over the products of my labour. However, Gheaus argues that a standard labour account of parental rights could not generate parental rights over one’s own birth child via gestation without ownership, since the labour would merely afford one a right to enjoy the goods of parenthood. At best, then, labour alone would generate a right to a child. But, Gheaus argues, not only do gestational mothers expend labour in the course of the pregnancy; they also develop emotional ties to the fetus. They ‘bond’ with it. This, Gheaus argues, coupled with labour, gives the birth mother parental rights over her birth child. Fathers, on her account, acquire rights over their birth child by contributing labour—in the form of antenatal support—during the course of the pregnancy. I argue that because ‘bonding’ is not an appropriately morally salient phenomenon, Gheaus’s account does not work unless it relies on a proprietary claim, and this is prima facie reason to reject the account. Further, the fact that it only confers parental rights on fathers by proxy also gives us reason to reject the account. I then offer a brief sketch of a more promising, positive account of parental rights.

Intertemporal Disagreement and Empirical Slippery Slope Arguments

One prevalent type of slippery slope argument has the following form: (1) by doing some initial act now, we will bring it about that we subsequently do some more extreme version of this act, and (2) we should not bring it about that we do this further act, therefore (3) we should not do the initial act. Such arguments are frequently regarded as mistaken, often on the grounds that they rely on speculative or insufficiently strong empirical premises. In this article I point out another location at which these arguments may go wrong: I argue that, in their standard form, the truth of their empirical premises constitutes evidence for the falsity of their normative premises. If we will, as predicted, do the further act in the future, this gives us at least a prima facie reason to believe that the performance of this further act would be good, and thus something we should try to bring about. I end by briefly assessing the dialectic implications of my argument. I delineate a subset of slippery slope arguments against which my objection may be decisive, consider how the proponents of such arguments may evade my objection by adding further premises, and examine the likely plausibility of these additional premises.

Advanced Topics: Induction

It is well known, since Goodman [1955], that principles of induction require a projectibility constraint. On the present account, such a constraint is inherited from the projectibility constraint on (A1)–(A3). It remains to be shown, however, that this derived constraint is the intuitively correct constraint. Let us define: (1.1) A concept B (or the corresponding property) is inductively projectible with respect to a concept A (or the corresponding property) iff ┌X is a set of A’s, and all the members of X are also B’s┐ is a prima facie reason for ┌A ⇒ B┐, and this prima facie reason would not be defeated by learning that there are non-B’s. A nomic generalization is projectible iff its consequent is inductively projectible with respect to its antecedent. What is needed is an argument to show that inductive projectibility is the same thing as projectibility. To make this plausible, I will argue that inductive projectibility has the same closure properties as those defended for projectibility in Chapter 3. Goodman introduced inductive projectibility with examples of nonprojectible concepts like grue and bleen, and the impression has remained that only a few peculiar concepts fail to be inductively projectible. That, however, is a mistake. It is not difficult to show that most concepts fail to be inductively projectible, inductive projectibility being the exception rather than the rule. This results from the fact that, just like projectibility, the set of inductively projectible concepts is not closed under most logical operations. In particular, I will argue below that although inductive projectibility is closed under conjunction, it is not closed under either disjunction or negation. That is, negations or disjunctions of inductively projectible concepts are not automatically inductively projectible. Just as for projectibility, we can argue fairly conclusively that inductive projectibility is closed under conjunction. More precisely, the following two principles hold: (1.2) If A and B are inductively projectible with respect to C, then (A&B) is inductively projectible with respect to C. (1.3) If A is inductively projectible with respect to both B and C, then A is inductively projectible with respect to (B&C).

Recapitulation

The purpose of this book is to clarify probability concepts and analyze the structure of probabilistic reasoning. The intent is to give an account that is precise enough to actually be useful in philosophy, decision theory, and statistics. An ultimate objective will be to implement the theory of probabilistic reasoning in a computer program that models human probabilistic reasoning. The result will be an AI system that is capable of doing sophisticated scientific reasoning. However, that takes us beyond the scope of the present book. The purpose of this chapter is to give a brief restatement of the main points of the theory of nomic probability and provide an assessment of its accomplishments. The theory of nomic probability has a parsimonious basis. This consists of two sets of principles. First, there are the epistemic principles (A3) and (D3):(A3) If F is projectible with respect to G and r > .5, then ┌prob(F/G) > r┐ is a prima facie reason for the conditional ┌Gc ⊃ Fc┐, the strength of the reason depending upon the value of r. (D3) If F is projectible with respect to H then ┌Hc & prob(F/G&H) < prob(F/G) ┐ is an undercutting defeater for rprob(F/G) > r┐ as a prima facie reason for ┌Gc ⊃ Fc┐. Second, there are some computational principles that generate a calculus of nomic probabilities. These principles jointly constitute the conceptual role of the concept of nomic probability and are the basic principles from which the entire theory of nomic probability follows. The epistemic principles presuppose a prior epistemological framework governing the interaction of prima facie reasons and defeaters. Certain aspects of that framework play an important role in the theory of nomic probability. For example, the principle of collective defeat is used recurrently throughout the book. The details of the epistemological framework are complicated, but they are not specific to the theory of probability. They are part of general epistemology. The computational principles are formulated in terms of what some will regard as an extravagant ontology of sets of possible objects and possible worlds. It is important to realize that this ontology need not be taken seriously.

Advanced Topics: Defeasible Reasoning

The principal novelty this book brings to probability theory is a sophisticated epistemology accommodating defeasible reasoning. It is this that makes the theory of nomic probability possible. Earlier theories lacked the conceptual framework of prima facie reasons and defeaters, and hence were unable to adequately formulate principles of probabilistic reasoning. Thus far, the book has relied upon a loosely formulated account of the structure of defeasible reasoning, but that must be tightened up before the theory can be implemented. This chapter gives a more rigorous account of defeasible reasoning and compares the present theory with some related work in AI. Reasoning begins from various kinds of inputs, which for convenience I will suppose to be encoded in beliefs. Crudely put, reasoning proceeds in terms of reasons. Reasons are strung together into arguments and in this way the conclusions of the arguments become justified. The general notion of a reason can be defined as follows: (2.1) A set of propositions {P1,...,Pn} is a reason for S to believe Q if and only if it is logically possible for S to be justified in believing Q on the basis of believing P1, ...,Pn. There are two kinds of reasons-defeasible and nondefeasible. Nondefeasible reasons are those reasons that logically entail their conclusions. For instance, (P&Q) is a nondefeasible reason for P. Such reasons are conclusive reasons. P is a defeasible reason for Q just in case P is a reason for Q, but it is possible to add additional information that undermines the justificatory connection. Such reasons are called ‘prima facie reasons’. This notion can be defined more precisely as follows: (2.2) P is a prima facie reason for S to believe Q if and only if P is a reason for S to believe Q and there is an R such that R is logically consistent with P but (P&R) is not a reason for S to believe Q.