Richard C. Jeffrey

The Philosophy of Rudolf Carnap

Part of a series of studies of contemporary philosophers, this volume focuses on Rudolf Carnap.

Studies in Inductive Logic and Probability

A bottle of especial utility is disclosed. The bottle may be made of synthetic material as polyvinyl chloride. The bottle is formed by the rotation of a faired generating line made up from a straight linear segment and arcs of selected radii and centers about a central longitudinal axis. The linear segment of the generating line is parallel with the axis and the arcs are tangent at their points of juncture with each other and with the linear segment. The generating line thus rotated defines a form from which a mold is readily and inexpensively made to produce a bottle having adequate strength. The bottle may be used to contain, in particular, carbonated and like beverages or liquids. The bottom of the bottle is interiorly convex reentrant shape and has an exterior integral diametral reinforcing rib.

Statistical Explanation vs. Statistical Inference

Hempel is not the first philosopher to have held that causal explanations are deductive inferences of a special sort: in the Posterior Analytics 1 Aristotle distinguishes a special sort of deductive inference — the demonstrative syllogism — in these terms: By demonstration I mean a syllogism productive of scientific knowledge, a syllogism, that is, the grasp of which is eo ipso such knowledge.

Dracula Meets Wolfman: Acceptance vs. Partial Belief

One of the things I’d like to see come out of this conference is a clarification of the issues between Isaac Levi and me.1 I take it that Levi’s scruples about partial belief and probability kinematics are not idiosyncratic, nor are my scruples about his work on acceptance, so that the matter may be of general interest. When Dracula meets Wolfman in the movies it is not simply I-and-thou: They gibber and slaver for all vampires and all werewolves everywhere. So let it be with us.

Conditioning, Kinematics, and Exchangeability

The change (“conditioning”) from prior P to posterior Q = P( |E) is appropriate only if it changes no probabilities conditionally on E. Under similar conditions a generalization of conditioning (“probability kinematics”) is appropriate when Q(E) < 1. That generalization is pretty nearly equivalent to ordinary conditioning on the extraordinary proposition that Q(E) has a certain value. Whether or not generalized conditioning is sensitive to the order in which successive changes are made depends on how the changes are set, e.g., by probabilities, or by ratios of probabilities. In a finitistic framework simple and generalized (“partial”) exchangeability are characterized and related to probability kinematics.

The logic of decision defended

The approach to decision theory floated in my 1965 book is reviewed (I), challenged in various related ways (II–V) and defended, firstad hoc (II–IV) and then by a general argument of Ellery Ellss (VI). Finally, causal decision theory (in a version sketched in VII) is exhibited as a special case of my 1965 theory, according to the Eellsian argument.

The Sure Thing Principle

The Sure Thing Principle (1), Dominance Principle (2), and Strong Independence Axiom (3) have been attacked and defended in various ways over the past 30 years. In the course of a survey of some of that literature, it is argued that these principles are acceptable iff suitably qualified.

Indefinite Probability Judgment: A Reply to Levi

Isaac Levi and I have different views of probability and decision making. Here, without addressing the merits, I will try to answer some questions recently asked by Levi (1985) about what my view is, and how it relates to his.

Alias Smith and Jones: The testimony of the senses

Probabilistic accounts of judgment can disappoint dogmatically rooted expectations, i.e., expectations rooted in cases where simple ac? ceptance and rejection are appropriate attitudes toward hypotheses, and where evidence can be expected to simply verify or falsify hypotheses. But probabilistic judgment, freed from the two endpoints, can rate hypotheses anywhere in the unit interval, and can do the same for evidence itself. Where the reliability of signs and witnesses is an issue, dogmatism must in some measure take account of probabilistic considerations; but the risk of paradox is then extreme. Here is such a case, presented as an epistemological parable that can also be read as a parable of scientific hypothesis-testing.

Justice, Political Liberalism, and Utilitarianism: Preference Aggregation after Harsanyi

Introduction Consider a group of people whose preferences satisfy the axioms of one of the current versions of utility theory, such as von Neumann–Morgenstern (1944), Savage (1954), or Bolker (1965)and Jeffrey (1965). There are political and economic contexts in which it is of interest to find ways of aggregating these individual preferences into a group preference ranking. The question then arises of whether methods of aggregation exist in which the groups preferences also satisfy the axioms of the chosen utility theory, while at the same time the aggregation process satisfies certain plausible conditions (e.g., the Pareto conditions introduced later). The answer to this question is sensitive to details of the chosen utility theory and method of aggregation. Much depends on whether uncertainty, expressed in terms of probabilities, is present in the framework and, if so, on how the probabilities are aggregated. The goal of this chapter is (a) to provide a conceptual map of the field of preference aggregation – with special emphasis, prompted by the occasion, on Harsanyis aggregation result and its relations to other results – and (b) to present a new problem (“flipping”), which leads to a new impossibility result. The story begins with some bad news, roughly fifty years old, about “purely ordinal” frameworks, in which probabilities play no role. Arrows General Possibility Theorem (1950, 1951, 1963) : No universally applicable nondictatorial method of aggregating individual preferences into group preferences can satisfy both the Pareto Preference condition (unanimous individual preferences are group preferences) and the condition of Independence of Irrelevant Alternatives (group preference between two prospects depends only on individual preferences between those same prospects) .