It is widely held that Bayesian decision theory is the final word on how a rational person should make decisions. However, Leonard Savage--the inventor of Bayesian decision theory--argued that it would be ridiculous to use his theory outside the kind of small world in which it is always possible to "look before you leap." If taken seriously, this view makes Bayesian decision theory inappropriate for the large worlds of scientific discovery and macroeconomic enterprise. When is it (...) correct to use Bayesian decision theory--and when does it need to be modified? Using a minimum of mathematics, Rational Decisions clearly explains the foundations of Bayesian decision theory and shows why Savage restricted the theory's application to small worlds. The book is a wide-ranging exploration of standard theories of choice and belief under risk and uncertainty. Ken Binmore discusses the various philosophical attitudes related to the nature of probability and offers resolutions to paradoxes believed to hinder further progress. In arguing that the Bayesian approach to knowledge is inadequate in a large world, Binmore proposes an extension to Bayesian decision theory--allowing the idea of a mixed strategy in game theory to be expanded to a larger set of what Binmore refers to as "muddled" strategies. Written by one of the world's leading game theorists, Rational Decisions is the touchstone for anyone needing a concise, accessible, and expert view on Bayesian decision making. (shrink)

In past years, the traditional Bayesian theory of rational decision making, based on subjective calculations of expected utility, has faced powerful attack from philosophers such as David Lewis and Brian Skyrms, who advance an alternative causal decision theory. The test they present for the Bayesian is exemplified in the decision problem known as 'Newcomb's paradox' and in related decision problems and is held to support the prescriptions of the causal theory. As well as his conclusions, (...) the concepts and methods of Professor Eells introduces in the course of his analyses have extensive implications, not solely for probability theorists narrowly conceived, but for economists, statisticians and psychologists concerned with decision making and the employment of Bayesian principles. They and their students will, in addition, find the early chapters of great use as a background and introduction to the subject as a whole. (shrink)

Prima facie, we make successful decisions as we act on and intervene in the world day-to-day. Epistemologists are often concerned with whether rationality is involved in such decision-making practices, and, if so, to what degree. Some, particularly in the post-structuralist tradition, argue that successful decision-making occurs via an existential leap into the unknown rather than via any determinant or criterion such as rationality. I call this view radical voluntarism (RV). Proponents of RV include those who subscribe to a (...) view they call Critical Complexity (CC). In this paper, I argue that CC presents a false dichotomy when it conceives of rationality in Cartesian – i.e. ideal and transcendental – terms, and then concludes that RV is the proper alternative. I then outline a pragmatist rationality informed by recent work in psychology on bounded rationality, ecological rationality, and specifically embodied rationality. Such a pragmatist rationality seems to be compatible with the tenets of post-structuralism, and can therefore replace RV in CC. (shrink)

This chapter contains sections titled: Introduction: Rational Decisions as an Ideal Rational Decision Making? Assumptions and Difficulties: Preferences, Outcome Spaces, and Probabilities in the World Reasons without Decisions What Kinds of Reasons? The Failure of RCT as a Unifying Principle The Failures of RCT and Rethinking Rationality.

As rationing decisions become more of an immediate reality for healthcare practitioners it is important to design mechanisms that facilitate carefully deliberated outcomes. No individual can be expected to be able to cover wide debate on their own, so an exercise has been designed that helps generate consensus decisions from diverse opinions. The exercise was piloted with two groups, an undergraduate medical class and the members of a general practice. Though the aims were different for each group, the tool was (...) useful to both for producing the desired outcomes. Expert and non-expert knowledge were drawn upon and rationing prioritisation lists regarding funding of infertility treatment were generated. A description of the exercise and the results produced by the two groups are provided, as well as the theoretical placement for the significance of forming consensus from diversity. (shrink)

How can we make rational decisions that involve transformative experiences, that is, experiences that can radically change our core preferences? L. A. Paul (2014) has argued that many decisions involving transformative experiences cannot be rational. However, Paul acknowledges that some traumatic events can be transformative experiences, but are nevertheless not an obstacle to rational decision-making. For instance, being attacked by hungry sharks would be a transformative experience, and yet, deciding not to swim with hungry sharks is (...) rational. Paul has tried to explain why decisions involving ‘sharky’ outcomes are an exception to the rule. However, her putative explanation has been criticized by Campbell and Mosquera (2020). In this paper, I offer a different solution to this problem. Roughly, I argue that transformative experiences give rise a problem for rational decision-making only if the decision can lead to satisfying some of our (new) core preferences, but can also frustrate other (new) core preferences. I also argue that agents can partially project what traumatic transformative experiences are like. (shrink)

In this study I discuss G. W. Leibniz's (1646-1716) views on rational decision-making from the standpoint of both God and man. The Divine decision takes place within creation, as God freely chooses the best from an infinite number of possible worlds. While God's choice is based on absolutely certain knowledge, human decisions on practical matters are mostly based on uncertain knowledge. However, in many respects they could be regarded as analogous in more complicated situations. In addition to (...) giving an overview of the divine decision-making and discussing critically the criteria God favours in his choice, I provide an account of Leibniz's views on human deliberation, which includes some new ideas. One of these concerns is the importance of estimating probabilities – in making decisions one estimates both the goodness of the act itself and its consequences as far as the desired good is concerned. Another idea is related to the plurality of goods in complicated decisions and the competition this may provoke. Thirdly, heuristic models are used to sketch situations under deliberation in order to help in making the decision. Combining the views of Marcelo Dascal, Jaakko Hintikka and Simo Knuuttila, I argue that Leibniz applied two kinds of models of rational decision-making to practical controversies, often without explicating the details. The more simple, traditional pair of scales model is best suited to cases in which one has to decide for or against some option, or to distribute goods among parties and strive for a compromise. What may be of more help in more complicated deliberations is the novel vectorial model, which is an instance of the general mathematical doctrine of the calculus of variations. To illustrate this distinction, I discuss some cases in which he apparently applied these models in different kinds of situation. These examples support the view that the models had a systematic value in his theory of practical rationality. (shrink)

Herein below I will try to set out certain innate traits of scientific rationality, by means of making a comparison between leading subjective and objective accounts of it in aspects representative for their explanatory potential. Scientific rationality might well be taken in as a system of specific norms, originating from, and upheld by, a scientific community; norms offering a choice of best decisions in a set of rival alternatives. Hence, a study may be developed up to the evolvement of a (...) uniform conception of scientific rationality and its variants. (shrink)

The objective of this paper is to construct an implementable theory of rational decision-making for cognitive agents subject to realistic resource constraints. It is argued that decision-making should select actions indirectly by selecting plans that prescribe them. It is also argued that although expected values provide the tool for evaluating plans, plans cannot be compared straightforwardly in terms of their expected values, and the objective of a realistic agent cannot be to find optimal plans. The theory of (...) Locally Global planning is proposed as a realistic alternative to standard "maximizing" theories of rational decision-making. (shrink)

The study’s main thesis is that respect for some moral values is a condition for methodologically rational decisions, namely, decisions which do not satisfy the condition are either not methodologically rational at all, or not fully rational. The paper shows supporting arguments for the thesis in terms of the philosophical theories by Aristotle, Immanuel Kant, Tadeusz Kotarbiński, Max Weber, Jean-Paul Sartre and some other thinkers. Their presentation undergoes phenomenological analysis of the phenomenon of decision making.

Abstract:The standard, Bayesian account of rational belief and decision is often argued to be unable to cope properly with severe uncertainty, of the sort ubiquitous in some areas of policy making. This paper tackles the question of what should replace it as a guide for rational decision making. It defends a recent proposal, which reserves a role for the decision maker’s confidence in beliefs. Beyond being able to cope with severe uncertainty, the account has strong (...) normative credentials on the main fronts typically evoked as relevant for rational belief and decision. It fares particularly well, we argue, in comparison to other prominent non-Bayesian models in the literature. (shrink)

Colman shows that normative theories of rational decision-making fail to produce rational decisions in simple interactive games. I suggest that well-formed theories are possible in local settings, keeping in mind that a good part of each game is the generation of a rational approach appropriate for that game. The key is rationality defined in terms of the game, not individual decisions.

The objective of this book is to produce a theory of rational decision making for realistically resource-bounded agents. My interest is not in “What should I do if I were an ideal agent?”, but rather, “What should I do given that I am who I am, with all my actual cognitive limitations?” The book has three parts. Part One addresses the question of where the values come from that agents use in rational decision making. The most (...) comon view among philosophers is that they are based on preferences, but I argue that this is computationally impossible. I propose an alternative theory somewhat reminiscent of Bentham, and explore how human beings actually arrive at values and how they use them in decision making. Part Two investigates the knowledge of probability that is required for decision-theoretic reasoning. I argue that subjective probability makes no sense as applied to realistic agents. I sketch a theory of objective probability to put in its place. Then I use that to define a variety of causal probability and argue that this is the kind of probability presupposed by rational decision making. So what is to be defended is a variety of causal decision theory. Part Three explores how these values and probabilities are to be used in decision making. In chapter eight, it is argued first that actions cannot be evaluated in terms of their expected values as ordinarily defined, because that does not take account of the fact that a cognizer may be unable to perform an action, and may even be unable to try to perform it. An alternative notion of “expected utility” is defined to be used in place of expected values. In chapter nine it is argued that individual actions cannot be the proper objects of decision-theoretic evaluation. We must instead choose plans, and select actions indirectly on the grounds that they are prescribed by the plans we adopt. However, our objective cannot be to find plans with maximal expected utilities. Plans cannot be meaningfully compared in that way. (shrink)

Rationality in decision making is commonly assessed by comparing choice performance against normative standards. We argue that such a performance-centered approach blurs the distinction between rational choice and adaptive behavior. Instead, rational choice should be assessed with regard to the way individuals make analytic decisions. We suggest that analytic decisions can be made in two different modes in which control processes are directed at different levels. In a RUN mode, thought is directed at controlling the operation of (...) a decision strategy. In the JUMP mode, the individual analyses the interpretation of the decision situation as well as the appropriateness of alternative strategies. We suggest that a decision should be considered “rational” when an individual is able to switch between these modes and balance their interaction. (shrink)

Le présent ouvrage collectif contient les Actes d'un colloque international bilingue sur l'action, les attitudes et la décision que nous avons organisé en hommage à notre regretté collègue J.-Nicolas Kaufmann à Trois-Rivières du 3 au 5 octobre 2002. L'ouvrage présente et discute d'hypothèses, d'enjeux et de théories contemporaines sur l'action, les attitudes, la rationalité et la décision. La première partie intitulée Pensées, actions et engagements contient des contributions de John Searle, Daniel Vanderveken, Candida Jaci de Sousa Melo et Raimo Tuomela (...) traitant de problèmes généraux de la philosophie de l'esprit et de l'action. Dans la deuxième partie de l'ouvrage intitulée Phénoménologie, ontologie et philosophie de l'esprit, nous avons regroupé, autour d'un texte de Nicolas Kaufmann, quatre études qui traitent diversement de la contribution de la phénoménologie classique, principalement de la phénoménologie de Husserl, à des questions centrales de la philosophie contemporaine dans les domaines de la philosophie de l'esprit, de la théorie de l'action et de l'ontologie formelle. La troisième partie de l'ouvrage, Causalité et naturalisme, réunit trois contributions qui portent sur des questions centrales de la philosophie contemporaine. Daniel Laurier se penche sur la question de savoir si le normativisme sémantique est compatible avec le naturalisme sémantique, alors qu'André Leclerc et Wilson Mendonça s'intéressent à la notion de causalité mentale et examinent différents arguments qui contestent le bien-fondé de cette notion. La dernière partie de l'ouvrage intitulée Rationalité et décision réunit trois contributions logico philosophiques de Storrs McCall, Mathieu Marion et Michel Paquette qui traitent de la rationalité des agents lors de leurs prises de décision et délibérations. (shrink)

Leibniz frequently argued that reasons are to be weighed against each other as in a pair of scales, as Professor Marcelo Dascal has shown in his article "The Balance of Reason." In this kind of weighing it is not necessary to reach demonstrative certainty – one need only judge whether the reasons weigh more on behalf of one or the other option However, a different kind of account about rational decision-making can be found in some of Leibniz's writings. (...) In his article "Was Leibniz's Deity an Akrates?" Professor Jaakko Hintikka has argued that Leibniz developed a new vectorial model for rational decisions which is better suited to complicated decisions, where values are complementary to each other. This model, related closely to his work in metaphysics and the philosophy of mind, is a heuristic device which helps in finding rational combinations - and in an ideal case an optimum - between plural inclinations to the good. I shall argue that Leibniz applies more or less implicitly both of these models in his practical rationality. In simple situations he applied the pair of scales model and in more complicated situations he applied the vectorial model. (shrink)

Being a formal and general as well as the most widely accepted approach to practical rationality, rational decision theory should be crucial for justifying rational morals. In particular, acting morally should also be rational in decision theoretic terms. After defending this thesis, in the critical part of the paper two strategies to develop morals following this insight are criticized: game theoretical ethics of cooperation and ethical intuitionism. The central structural objections to ethics of cooperation are (...) that they too directly aim at the rationality of moral action and that they to do not encompass moral values or a moral desirability function. The constructive half of the paper takes up these criticisms by developing a two-part strategy to bring rationality and morals in line. The first part is to define ‘moral desirability’. This is done, using multi-attribute utility theory, by equating several adequate components of an individual’s comprehensive utility function with the moral desirability function. The second part is to introduce mechanisms, institutions, in particular socially valid moral norms, that provide further motivation for acting in accordance with morals. (shrink)

This article surveys the latest research on risky-choice framing effects, focusing on the implications for rational decision-making. An influential program of psychological research suggests that people's judgements and decisions depend on the way in which information is presented, or ‘framed’. In a central choice paradigm, decision-makers seem to adopt different preferences, and different attitudes to risk, depending on whether the options specify the number of people who will be saved or the corresponding number who will die. It (...) is standardly assumed that such responses violate a foundational tenet of rational decision-making, known as the principle of description invariance. We discuss recent theoretical and empirical research that challenges the dominant ‘irrationalist’ narrative. These approaches typically pay close attention to how decision-makers represent decision problems (including their interpretation of numerical quantifiers or predicate choice) and they highlight the need for a more robust characterization of the description invariance principle. We conclude by indicating avenues for future research that could bring us closer to a complete—and potentially rationalizing—explanation of framing effects. (shrink)

L.A. Paul has recently argued that, on the standard model of rationality, individuals cannot make rational decisions about whether to have a child or not. In this paper, I show that Paul’s arguments do not plausibly demonstrate that the standard model of rationality precludes rational decisions to have a child. I argue that there are phenomenal and non-phenomenal values that can be used to determine the value that having a child will have for us and, in turn, that (...) can be used to make rational decisions about whether to have a child or not. I also argue that we can have an approximate idea of what it is like for us to have a child, even before we have a child and that, on the standard model, this is sufficient to make rational decisions to have a child. (shrink)

Taking Savage's subjective expected utility theory as a starting point, this thesis distinguishes three types of uncertainty which are incompatible with Savage's theory for small worlds: ambiguity, option uncertainty and state space uncertainty. Under ambiguity agents cannot form a unique and additive probability function over the state space. Option uncertainty exists when agents cannot assign unique consequences to every state. Finally, state space uncertainty arises when the state space the agent constructs is not exhaustive, such that unforeseen contingencies can occur. (...) Chapter 2 explains Savage's notions of small and large worlds, and shows that ambiguity, option and state space uncertainty are incompatible with the small world representation. The chapter examines whether it is possible to reduce these types of uncertainty to one another. Chapter 3 suggests a definition of objective ambiguity by extending Savage's framework to include an exogenous likelihood ranking over events. The definition allows for a precise distinction between ambiguity and ambiguity attitude. The chapter argues that under objective ambiguity, ambiguity aversion is normatively permissible. Chapter 4 gives a model of option uncertainty. Using the two weak assumptions that the status quo is not uncertain, and that agents are option uncertainty averse, we derive status quo bias, the empirical tendency for agents to choose the status quo over other available alternatives. The model can be seen as rationalising status quo bias. Chapter 5 gives an axiomatic characterisation and corresponding representation theorem for the priority heuristic, a heuristic which predicts binary decisions be- tween lotteries particularly well. The chapter analyses the normative implications of this descriptive model. Chapter 6 defends the pluralist view of decision theory this thesis assumes. The chapter discusses possible applications of the types of uncertainty defined in the thesis, and concludes. (shrink)

The rational-decision approach is superior to the associative-learning approach of Cook et al. at explaining why mirror neurons (MNs) fire or do not fire – even when the stimulus is the same. The rational-decision approach is superior because it starts with the analysis of the intention of the organism, i.e., with the identification of the specific objective or goal that the organism is trying to maximize.

Nicholas J.J. Smith (2014) has argued that there are different kinds of degrees of belief, but that they must be fused into one ‘all kinds considered’ degree of belief. We provide an example which shows that different kinds of degrees of belief can have diverging impacts on the rationality of a decision: there are cases in which two rational subjects with identical preferences and the same ‘all kinds considered’ degree of belief make different decisions. Thus, different kinds of (...) degrees of belief should not be merged into a single degree-of-belief function. (shrink)

ABSTRACT Is uncertainty about preferences rationally possible? And if so, does it matter for rational decision? It is argued that uncertainty about preferences is possible and should play the same role in rational decision-making as uncertainty about worldly facts. The paper develops this hypothesis and defends it against various objections.

This is a selection of the most important work of Edna Ullmann-Margalit, an unorthodox and deeply original philosopher whose work illuminated the largest mysteries of human life. It centres on two questions: How do people proceed when they cannot act on the basis of reasons, or project likely consequences? How is social order possible?

Chapter 1 Who this book is for and who it is not for1 There are already too many books offering solutions to the problems of the health service. ...

Recent work has formally linked the traditional axiomatisation of incomplete preferences à la Anscombe-Aumann with the theory of desirability developed in the context of imprecise probability, by showing in particular that they are the very same theory. The equivalence has been established under the constraint that the set of possible prizes is finite. In this paper, we relax such a constraint, thus de facto creating one of the most general theories of rationality and decision making available today. We provide (...) the theory with a sound interpretation and with basic notions, and results, for the separation of beliefs and values, and for the case of complete preferences. Moreover, we discuss the role of conglomerability for the presented theory, arguing that it should be a rationality requirement under very broad conditions. (shrink)

This volume explores from multiple perspectives the subtle and interesting relationship between the theory of rational choice and Darwinian evolution. In rational choice theory, agents are assumed to make choices that maximize their utility; in evolution, natural selection 'chooses' between phenotypes according to the criterion of fitness maximization. So there is a parallel between utility in rational choice theory and fitness in Darwinian theory. This conceptual link between fitness and utility is mirrored by the interesting parallels between (...) formal models of evolution and rational choice. The essays in this volume, by leading philosophers, economists, biologists and psychologists, explore the connection between evolution and rational choice in a number of different contexts, including choice under uncertainty, strategic decision making and pro-social behaviour. They will be of interest to students and researchers in philosophy of science, evolutionary biology, economics and psychology. (shrink)

In its classical conception, game theory aspires to be a determinate decision theory for games, understood as elements of a structurally specified domain. Its aim is to determine for each game in the domain a complete solution to each player's decision problem, a solution valid for all real-world instantiations, regardless of context. "Permissiveness" would constrain the theory to designate as admissible for a player any conjecture consistent with the function's designation of admissible strategies for the other players. Given (...) permissiveness and other appropriate constraints, solution sets must contain only Nash equilibria and at least one pure-strategy equilibrium, and there is no solution to games in which no symmetry invariant set of pure-strategy equilibria forms a Cartesian product. These results imply that the classical program is unrealizable. Moreover, the program is implicitly committed to permissiveness, through its common-knowledge assumptions and its commitment to equilibrium. The resulting incoherence deeply undermines the classical conception in a way that consolidates a long series of contextualist criticisms. (shrink)

Issues of resource allocationResource allocation, triageTriage, and rationingRationing decisions are common in the context of disasters and public healthPublic health emergencies, such as pandemics. However, to date, the majorityMajority of the literature focuses on an adult population with very little attention given to a pediatric population or to a population that may be mixed: adults and children. Furthermore, decisions of rationingRationing scarce resources do not only occur during disasters and other wide-scale emergencies. Such decisions are commonplace in pediatric organ transplantation (...) and can creep into areas of experimental medicine, such as xenotransplantation. This chapter explicates differences between pediatric and adult triageTriage decisions by first looking at the trifold issues of resource allocationResource allocation, triageTriage, and rationingRationing decisions mainly in the context of a disaster situation or public healthPublic health emergency. However, the issues of pediatric organ transplantation, health disparitiesHealth disparities, and experimental medicine will also be covered. (shrink)

In personal and public affairs alike we constantly confront the need for deciding among available alternatives. Sensible Decisions synthesizes Nicholas Rescher's contribution to this discussion over the years. Rescher's prime aim is to illuminate some of the theoretical complications and perplexities that characterize rational procedure in matters of decision making at the public policy level.

G. W. Leibniz developed a new model for rational decision-making which is suited to complicated decisions, where goods do not rule each other out, but compete with each other. In such cases the deliberator has to consider all of the goods and pick the ones that contribute most to the desired goal which in Leibniz’s system is ultimately the advancement of universal perfection. The inclinations to particular goods can be seen as vectors leading to different directions much like (...) forces in Leibniz’s dynamics. The vectorial model of rational decision-making is related to Leibniz’s work with metaphysical physics and the calculus of variations and is a heuristic tool which helps in finding reasonable combinations – in ideal cases optimums - between competing goods. By applying the model, the decision-maker can map and compare outcomes of combinations of goods in question and practice a kind of pseudo-mechanical arithmetic of reasons. A central feature of the model is the possibility to employ geometrical figures to help the conceptualization. In this paper I present the vectorial model, examine its applications in practical cases from political theory, jurisprudence and ethics Leibniz presented, and compare the model to recent theories of acting under uncertainty, such as bounded rationality and optimizing under constraints. (shrink)

SummaryI contend on both theoretical and historical grounds that quantitative risk assessment is relevant for policy determination only as a cost estimate. In particular, it provides a method for estimating the costs of a hypothetical insurance policy against the potential liabilities associated with a given course of action. It is not relevant to the question of rational choice under risk.RésuméJe montre, en partant d'arguments aussi bien théoriques qu'historiques, que le calcul quanti‐tatif des risques n'aide à la détermination d'une politique (...) à suivre qu'en tant qu'estimation des coûts. En particulier, il fournit une méthode pour estimer les primes d'une police hypothétique d'assurance contre les responsabilites potentielles associées à une suite donnée d'actions. 11 ne permet pas un choix rationnel dans des situations comportant des risques.ZusammenfassungIch argumentiere, sowohl aus theoretischen als auch aus historischen Gründen, dass eine quantitative Risikoberechnung für die Wahl einer Handlungsweise nur als Kostenschätzung relevant ist. Namentlich bietet sie eine Methode, um die Prämie einer Versicherungspolice gegen pot‐entielle Haftbarkeit, welche mit den Vorgängen eines Aktionsverlaufs verbunden ist, zu bestim‐men. Bei der Frage einer rationalen Wahl in einer Risikosituation ist sie nicht relevant. (shrink)

Nudging is a tool of libertarian paternalism. It involves making use of certain psychological tendencies in order to help people make better decisions without restricting their freedom. However, some have argued that nudging is objectionable because it interferes with, or undermines, the rational decision-making of the nudged agents. Opinions differ on why this is objectionable, but the underlying concerns appear to begin with nudging’s threat to rational decision-making. Those who discuss this issue do not make it (...) clear to what this threat to rationality amounts. In this paper I evaluate what effect nudging has on our decision-making and I argue that it does not typically interfere with our rationality in a problematic way. Perhaps nudging is objectionable for other reasons, but we should not argue that nudging is objectionable based on concerns about rational decision-making. (shrink)

Absolute and relative outcome measures measure a treatment’s effect size, purporting to inform treatment choices. I argue that absolute measures are at least as good as, if not better than, relative ones for informing rational decisions across choice scenarios. Specifically, this dominance of absolute measures holds for choices between a treatment and a control group treatment from a trial and for ones between treatments tested in different trials. This distinction has hitherto been neglected, just like the role of absolute (...) and baseline risks in rational decision-making that my analysis reveals. Recognizing both aspects advances the discussion on reporting outcome measures. (shrink)

This book review describes and evaluates John Pollock's view about rational decision-making.

This monograph is a collection of conference contributions chosen by the editors who led a three-year project on evolution, cooperation, and rationality. The collected works are held together by a six-page introduction identifying common strands and differences of positions in the different chapters. Since no two chapters have a common author, the chapters do not build on each other. Rather, they offer a variety of perspectives on a number of different aspects of rationality and evolution. The monograph thus does not (...) offer a unified account of evolution and rationality despite the possibly somewhat misleading title, nor is there a clearly identifiable overarching theme that runs through the entire book. (shrink)

Balancing implies a comparison among goods, values, principles and rights that cannot be ranked on a single scale of measurement, ie there is no unequivocal measuring unit applicable to all of them. In such situations, it is common to state that one has to compare incommensurable things. Indeed, this issue has been mentioned by several authors as a strong reason in favour of abandoning balancing (and proportionality) as a rational form of judicial argumentation and decision-making. My article aims (...) at arguing that this objection is based on fallacious assumptions concerning the relations among three concepts: incommensurability, incomparability and balancing. Initially, what is at stake is the analysis of the connection between comparing values (or principles) and commensurability. The results of this initial analysis were then used to provide greater analytical strength to the specific debate on balancing and comparing rights in order to show that incommensurability does not imply incomparability and that rational decisions are possible even when incommensurable values are at stake. Since balancing (and proportionality) implies comparisons, and since constitutional principles are doubtlessly incommensurable (for there is no common metric to measure them), arguing for the comparability of incommensurable principles is an unavoidable step if one aims at demonstrating that balancing may be a rational procedure after all. (shrink)