Isaac Levi

Subjunctives, Dispositions and Chances

X says ‘It is probable that h’ and Y says ‘It is improbable that h’. No doubt X and Y disagree in some ways. In particular, they disagree in the way they evaluate h with respect to credal (or personal) probability to be used in practical deliberation and scientific inquiry in computing expectations.

The covenant of reason : rationality and the commitments of thought

1. Rationality and commitment 2. Rationality, prediction and autonomous choice 3. The logic of full belief 4. Consequentialism and sequential choice 5. Prediction, deliberation and correlated equilibrium 6. On indeterminate probabilities 7. Consensus as shared agreement and outcome of inquiry 8. Compromising Bayesianism: a plea for indeterminacy 9. Pareto unanimity and consensus 10. The paradoxes of Allais and Ellsberg 11. Conflict and inquiry 12. The ethics of controversy.

Imprecision and Indeterminacy in Probability Judgment

Bayesians often confuse insistence that probability judgment ought to be indeterminate (which is incompatible with Bayesian ideals) with recognition of the presence of imprecision in the determination or measurement of personal probabilities (which is compatible with these ideals). The confusion is discussed and illustrated by remarks in a recent essay by R. C. Jeffrey.

The Paradoxes of Allais and Ellsberg

In The Enterprise of Knowledge (Levi, 1980a), I proposed a general theory of rational choice which I intended as a characterization of a prescriptive theory of ideal rationality. A cardinal tenet of this theory is that assessments of expected value or expected utility in the Bayesian sense may not be representable by a numerical indicator or indeed induce an ordering of feasible options in a context of deliberation. My reasons for taking this position are related to my commitment to the inquiry-oriented approach to human knowledge and valuation favored by the American pragmatists, Charles Peirce and John Dewey. A feature of any acceptable view of inquiry ought to be that during an inquiry points under dispute ought to be kept in suspense pending resolution through inquiry.

NEWCOMB'S MANY PROBLEMS

Newcomb’s paradox rests on two arguments one appealing to the principle of maximizing expected utility and one appealing to dominance in order to generate conflicting recommendations in certain kinds of choice situations. In my essay, I argue that the applications of the principle of maximizing expected utility and of the domi-nance principle are both fallacious and that the specification of the decision problem is too indeterminate to render a verdict between the two options considered. I also show that if Nozick’s case for invoking the dominance principle is taken seriously, it leads to contradictions.

Two notions of epistemic validity

How to accept a conditional? F. P. Ramsey proposed the following test in (Ramsey 1990).(RT) ‘If A, then B’ must be accepted with respect to the current epistemic state iff the minimal hypothetical change of it needed to accept A also requires accepting B.In this article we propose a formulation of (RT), which unlike some of its predecessors, is compatible with our best theory of belief revision, the so-called AGM theory (see (Gärdenfors 1988), chapters 1–5 for a survey). The new test, which, we claim, encodes some of the crucial insights defended by F. P. Ramsey in (Ramsey 1990), is used to study the conditionals epistemically validated by the AGM postulates. Our notion of validity (PV) is compared with the notion of negative validity (NV) used by Gärdenfors in (Gärdenfors 1988). It is observed that the notions of PV and NV will in general differ and that when these differences arise it is the notion of PV that is preferable. Finally we compare our formulation of the Ramsey test with a previous formulation offered by Gärdenfors (GRT). We show that any attempt to interpret (GRT) as delivering acceptance conditions for Ramseys conditionals is doomed to failure.

Value Commitments, Value Conflict, and the Separability of Belief and Value

Leeds (1990) levels an objection against the criterion of rational choice I have proposed (Levi 1997, Ch. 6; 1980; 1986), pointing out that the criterion is sensitive to the way possible consequences are partitioned. Seidenfeld, Kadane and Schervish (1989) call into question the defense of the cross product rule by appeal to Pareto Unanimity Principles that I had invoked in my 1986. I offer clarifications of my proposals showing that the difference between my views and those of my critics concerns the extent to which full belief, probabilistic belief, and value judgment are separable.

TRUTH, FALLIBILITY AND THE GROWTH OF KNOWLEDGE*

According to a familiar story, beliefs qualify as knowledge only if they can be justified on the basis of impeccable first premisses via equally immaculate first principles. The story has no truth to it. Centuries of criticism suggest that our interesting beliefs are born on the wrong side of the blanket.

Money Pumps and Diachronic Books

The idea that rational agents should have acyclic preferences and should obey conditionalization has been defended on the grounds that otherwise an agent is threatened with becoming a “money pump.” This essay argues that such arguments fail to prove their claims.

Imprecise and Indeterminate Probabilities

Bayesian advocates of expected utility maximization use sets of probability distributions to represent very different ideas. Strict Bayesians insist that probability judgment is numerically determinate even though the agent can represent such judgments only in imprecise terms. According to Quasi-Bayesians rational agents may make indeterminate subjective probability judgments. Both kinds of Bayesians require that admissible options maximize expected utility according to some probability distribution. Quasi-Bayesians permit the distribution to vary with the context of choice. Maximalists allow for choices that do not maximize expected utility against any distribution. Maximiners mandate what maximalists allow. This paper defends the quasi-Bayesian view against strict Bayesians, on the one hand, and maximalists and maximiners, on the other.