# Verisimilitude

Edited by Gustavo Cevolani (IMT School For Advanced Studies Lucca)
 Summary Truth is the aim of inquiry, but some theories seem to better approximate that goal than others. One may think, for instance, that Copernicus’ model of the solar system is closer to the truth than Ptolemy’s. Since Copernicus assumed that planetary orbits were circles, his theory is, strictly speaking, false. Thus, we have here a case of a false theory which better approximates the truth than another false theory. Moreover, Copernicus’ theory also seems better than the plain claim that planets move in orbits: so, false propositions may sometimes be more verisimilar even than true but uninformative ones. This suggests that verisimilitude (or truthlikeness, as it is also known) is a mixture of truth and informative content: a theory is verisimilar when it tells many things about the world, and many of these things are true. Explicating this intuition in a rigorous way amounts to solving the so-called logical problem of truthlikeness. In normal circumstances, we simply don’t know what the truth about a given matter is. Thus, we cannot directly assess the relative verisimilitude of competing theories. However, we can estimate their verisimilitude on the basis of available evidence: explaining exactly how this can be done means answering to the so-called epistemic problem of truthlikeness. Interestingly, estimated verisimilitude doesn’t follow the rules of probability. In particular, it may be that a theory with low probability is estimated as highly truthlike; and, a logically stronger theory may be estimated as more verisimilar than a logically weaker one. This makes (estimated) verisimilitude a mathematically less well-behaved notion than probability; still, it provides the philosopher of science with a flexible and useful tool to analyze such issues as theory change, scientific progress, convergence to the truth, and the realism/antirealism debate.
 Key works The notion of verisimilitude was first introduced, and clearly distinguished from probability, by Popper 1962 (see also Popper 1972 and Popper 1983), who also provided the first formal definition of truthlikeness. Ten years later, Tichý 1974 and Miller 1974 independently proved that Popper’s definition was untenable. This triggered the still ongoing post-Popperian research program on explicating verisimilitude, which currently include a number of different, and partially conflicting, proposals. These can be classified within three different perspectives (Zwart 2001, Oddie 2014): the content approach (Miller 1977, Miller 2006; Kuipers 1987), the likeness or similarity approach (Oddie 1986, Niiniluoto 1987), and the consequence approach (Schurz & Weingartner 1987, Schurz & Weingartner 2010). All such approaches address at least the logical problem of truthlikeness; for discussions of the epistemic problem see especially Niiniluoto 1987 and Kuipers 2000.
 Introductions Niiniluoto 1998 provides an excellent survey and discussion of the main accounts of verisimilitude; a more recent survey is given by Oddie 2014. Book-length treatments include Oddie 1986, Niiniluoto 1987, the collection edited by Kuipers 1987, Kieseppä 1996, Kuipers 2000 (parts III-IV), and Zwart 2001. Cevolani & Tambolo 2013  is a gentle introduction to the methodological applications of the notion of truthlikeness.
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Verisimilitude and the Dynamics of Scientific Research Programmes.Jesús P. Zamora Bonilla - 2002 - Journal for General Philosophy of Science / Zeitschrift für Allgemeine Wissenschaftstheorie 33 (2):349-368.
Some peculiarities of the evaluation of theories within scientific research programmes and of the assessing of rival SRPs are described assuming that scientists try to maximise an ‘epistemic utility function’ under economic and institutional constraints. Special attention is given to Lakatos' concepts of ‘empirical progress’ and ‘theoretical progress’. A notion of ‘empirical verisimilitude’ is defended as an appropriate utility function. The neologism ‘methodonomics’ is applied to this kind of studies.
Scientific Progress: Why Getting Closer to Truth is Not Enough.Moti Mizrahi - forthcoming - International Studies in the Philosophy of Science.
The aim of this discussion note is to contribute to the ongoing debate over the nature of scientific progress. I argue against the semantic view of scientific progress, according to which scientific progress consists in approximation to truth or increasing verisimilitude. If the semantic view of scientific progress were true, then scientists would make scientific progress simply by arbitrarily adding true disjuncts to their hypotheses or theories. Given that it is not the case that scientists would make scientific progress simply (...)
Empirical Progress and Truth Approximation by the ‘Hypothetico-Probabilistic Method’.Theo A. F. Kuipers - 2009 - Erkenntnis 70 (3):313-330.
Three related intuitions are explicated in this paper. The first is the idea that there must be some kind of probabilistic version of the HD-method, a 'Hypothetico-Probabilistic method', in terms of something like probabilistic consequences, instead of deductive consequences. According to the second intuition, the comparative application of this method should also be functional for some probabilistic kind of empirical progress, and according to the third intuition this should be functional for something like probabilistic truth approximation. In all three cases, (...)
Is Science Progressive. [REVIEW]Graham Oddie - 1987 - British Journal for the Philosophy of Science 38 (2):272-276.
The Concept of Truth in a Historistic Theory of Science.Kurt Hübner - 1980 - Studies in History and Philosophy of Science Part A 11 (2):145-151.
Truthlikeness and the Lottery Paradox Via the Preface Paradox.Simon D'Alfonso - 2018 - Australasian Journal of Philosophy 96 (2):391-397.
In a 2017 AJP paper, Cevolani and Schurz propose a novel solution to the Preface Paradox that appeals to the notion of expected truthlikeness. This discussion note extends and analyses their approach by applying it to the related Lottery Paradox.
A Partial Consequence Account of Truthlikeness.Gustavo Cevolani & Roberto Festa - 2018 - Synthese:1-20.
Popper’s original definition of truthlikeness relied on a central insight: that truthlikeness combines truth and information, in the sense that a proposition is closer to the truth the more true consequences and the less false consequences it entails. As intuitively compelling as this definition may be, it is untenable, as proved long ago; still, one can arguably rely on Popper’s intuition to provide an adequate account of truthlikeness. To this aim, we mobilize some classical work on partial entailment in defining (...)
What Accuracy Could Not Be.Graham Oddie - 2017 - British Journal for the Philosophy of Science:axx032.
Two different programs are in the business of explicating accuracy—the truthlikeness program and the epistemic utility program. Both assume that truth is the goal of inquiry, and that among inquiries that fall short of realizing the goal some get closer to it than others. TL theorists have been searching for an account of the accuracy of propositions. EU theorists have been searching for an account of the accuracy of credal states. Both assume we can make cognitive progress in an inquiry (...)
Toward Truthlikeness in Historiography.Oliver Laas - 2016 - European Journal of Pragmatism and American Philosophy 8 (2).
Belief Merging with the Aim of Truthlikeness.Simon D’Alfonso - 2016 - Synthese 193 (7):2013-2034.
The merging/fusion of belief/data collections in propositional logic form is a topic that has received due attention within the domains of database and AI research. A distinction can be made between two types of scenarios to which the process of merging can be applied. In the first type, the collections represent preferences, such as the voting choices of a group of people, that need to be aggregated so as to give a consistent result that in some way best represents the (...)
Optimistic Realism About Scientific Progress.Ilkka Niiniluoto - 2015 - Synthese 194 (9):3291-3309.
Scientific realists use the “no miracle argument” to show that the empirical and pragmatic success of science is an indicator of the ability of scientific theories to give true or truthlike representations of unobservable reality. While antirealists define scientific progress in terms of empirical success or practical problem-solving, realists characterize progress by using some truth-related criteria. This paper defends the definition of scientific progress as increasing truthlikeness or verisimilitude. Antirealists have tried to rebut realism with the “pessimistic metainduction”, but critical (...)
Scientific Progress Without Increasing Verisimilitude: In Response to Niiniluoto.Darrell Patrick Rowbottom - 2015 - Studies in History and Philosophy of Science Part A 51:100-104.
First, I argue that scientific progress is possible in the absence of increasing verisimilitude in science's theories. Second, I argue that increasing theoretical verisimilitude is not the central, or primary, dimension of scientific progress. Third, I defend my previous argument that unjustified changes in scientific belief may be progressive. Fourth, I illustrate how false beliefs can promote scientific progress in ways that cannot be explicated by appeal to verisimilitude.
Dovetailing Belief Base Revision with (Basic) Truth Approximation.T. A. F. Kuipers - 2014 - In E. Weber, D. Wouters & J. Meheus (eds.), Logic, Reasoning, and Rationality. Logic, Argumentation & Reasoning (Interdisciplinary Perspectives from the Humanities and Social Sciences), vol 5. Dordrecht: Springer. pp. 77-93.
Scientific Progress as Increasing Verisimilitude.Ilkka Niiniluoto - 2014 - Studies in History and Philosophy of Science Part A 46:73-77.
According to the foundationalist picture, shared by many rationalists and positivist empiricists, science makes cognitive progress by accumulating justified truths. Fallibilists, who point out that complete certainty cannot be achieved in empirical science, can still argue that even successions of false theories may progress toward the truth. This proposal was supported by Karl Popper with his notion of truthlikeness or verisimilitude. Popper’s own technical definition failed, but the idea that scientific progress means increasing truthlikeness can be expressed by defining degrees (...)
Scientific Progress as Increasing Verisimilitude.Ilkka Niiniluoto - 2014 - Studies in History and Philosophy of Science Part A 46:73-77.
According to the foundationalist picture, shared by many rationalists and positivist empiricists, science makes cognitive progress by accumulating justified truths. Fallibilists, who point out that complete certainty cannot be achieved in empirical science, can still argue that even successions of false theories may progress toward the truth. This proposal was supported by Karl Popper with his notion of truthlikeness or verisimilitude. Popper’s own technical definition failed, but the idea that scientific progress means increasing truthlikeness can be expressed by defining degrees (...)
Why Are Good Theories Good? Reflections on Epistemic Values, Confirmation, and Formal Epistemology.Jesús Zamora-Bonilla - 2013 - Synthese 190 (9):1533-1553.
Franz Huber’s (2008a) attempt to unify inductivist and hypothetico-deductivist intuitions on confirmation by means of a single measure are examined and compared with previous work on the theory of verisimilitude or truthlikeness. The idea of connecting ‘the logic of confirmation’ with ‘the logic of acceptability’ is also critically discussed, and it is argued that ‘acceptability’ takes necessarily into account some pragmatic criteria, and that at least two normative senses of ‘acceptability’ must be distinguished: ‘acceptable’ in the sense of ‘being allowed (...)
Bayesian Inductive Logic, Verisimilitude, and Statistics.R. Festa - 2011 - In D. M. Gabbay & J. Woods (eds.), Handbook of the Philosophy of Science: Philosophy of Statistics. North Holland. pp. 473--490.
Revising Beliefs Towards the Truth.Ilkka Niiniluoto - 2011 - Erkenntnis 75 (2):165-181.
Belief revision (BR) and truthlikeness (TL) emerged independently as two research programmes in formal methodology in the 1970s. A natural way of connecting BR and TL is to ask under what conditions the revision of a belief system by new input information leads the system towards the truth. It turns out that, for the AGM model of belief revision, the only safe case is the expansion of true beliefs by true input, but this is not very interesting or realistic as (...)
Basic and Refined Nomic Truth Approximation by Evidence-Guided Belief Revision in AGM-Terms.Theo Kuipers - 2011 - Erkenntnis 75 (2):223-236.
Straightforward theory revision, taking into account as effectively as possible the established nomic possibilities and, on their basis induced empirical laws, is conducive for (unstratified) nomic truth approximation. The question this paper asks is: is it possible to reconstruct the relevant theory revision steps, on the basis of incoming evidence, in AGM-terms? A positive answer will be given in two rounds, first for the case in which the initial theory is compatible with the established empirical laws, then for the case (...)
Introduction and Overview.Theo Kuipers & Gerhard Schurz - 2011 - Erkenntnis 75 (2):151-163.
Introduction and Overview Content Type Journal Article Category Introduction Pages 151-163 DOI 10.1007/s10670-011-9288-9 Authors Theo Kuipers, Faculty of Philosophy, University of Groningen, Groningen, The Netherlands Gerhard Schurz, Department of Philosophy, University of Duesseldorf, Universitaetsstrasse 1, Geb. 23.21, 40225 Duesseldorf, Germany Journal Erkenntnis Online ISSN 1572-8420 Print ISSN 0165-0106 Journal Volume Volume 75 Journal Issue Volume 75, Number 2.
The Development of the Hintikka Program.Ilkka Niiniluoto - 2011 - In Dov M. Gabbay, John Woods & Stephan Hartmann (eds.), Handbook of the History of Logic. Elsevier. pp. 311-356.
Scientific Progress.I. Niiniluoto - 2011 - In Edward N. Zalta (ed.), The Stanford Encyclopedia of Philosophy.
Theory Change, Truthlikeness, and Belief Revision.Ilkka Niiniluoto - 2010 - In M. Dorato M. Suàrez (ed.), Epsa Epistemology and Methodology of Science. Springer. pp. 189--199.
Comparative Realism as the Best Response to Antirealism.T. A. F. Kuipers - 2009 - In C. Glymour, W. Wei & D. Westerstahl (eds.), Logic, Methodology and Philosophy of Science. Proceedings of the Thirteenth International Congress. King’s College Publications. pp. 221--250.
Truthlikeness.G. Oddie - 2008 - In Martin P. Curd (ed.), The Routledge Companion to Philosophy of Science. pp. 478--488.
The Qualitative and Statistical Verisimilitude of Qualitative Theories.R. Festa - 2007 - la Nuova Critica 47:91--114.
Logically Equivalent--But Closer to the Truth.R. A. Sorensen - 2007 - British Journal for the Philosophy of Science 58 (2):287-297.
Verisimilitude has the potential to deepen the understanding of mathematical progress, the principle of charity, and the psychology of regret. One obstacle is the widely held belief that two statements can vary in truthlikeness only if they vary in what they entail. This obstacle is removed with four types of counterexamples. The first concerns necessarily coextensive measurements that differ only with respect to their units. The second class of counterexamples is composed of mathematical falsehoods. The third class features inconsistent scientific (...)
Abduction and Scientific Realism.Ilkka Niiniluoto - 2007 - The Proceedings of the Twenty-First World Congress of Philosophy 12:137-142.
Many scientific realists think that the best reasons for scientific theories are abductive, i.e., must appeal to what is also called inference to the best explanation (IBE), while some anti-realists have argued that the use of abduction in defending realism is question-begging, circular, or incoherent. This paper studies the idea that abductive inference can be reformulated by taking its conclusion to concern the truthlikeness of a hypothetical theory on the basis of its success in explanation and prediction. The strength of (...)
Out of Error: Further Essays on Critical Rationalism.D. Miller - 2006 - Ashgate Publishing.
Truthlikeness.I. Niiniluoto - 2006 - In Sahotra Sarkar & Jessica Pfeifer (eds.), The Philosophy of Science: An Encyclopedia. Routledge. pp. 854--857.
For Better, for Worse: Comparative Orderings on States and Theories.I. C. Burger & J. Heidema - 2005 - In R. Festa, A. Aliseda & J. Peijnenburg (eds.), Confirmation, Empirical Progress, and Truth Approximation. Essays in Debate with Theo ¸Iteauthorkuipers2000. Rodopi. pp. 459--488.
Abduction and Truthlikeness.Ilkka Niiniluoto - 2005 - In Roberto Festa, Atocha Aliseda & Jeanne Peijnenburg (eds.), Confirmation, Empirical Progress and Truth Approximation. Rodopi. pp. 255--275.
Content and Likeness Definitions of Truthlikeness.I. Niiniluoto - 2003 - In J. Hintikka, T. Czarnecki, K. Kijania-Placek, A. Rojszczak & T. Placek (eds.), Philosophy and Logic: In Search of the Polish Tradition. Essays in Honor of Jan Wole’Nski on the Occasion of His 60th Birthday. Kluwer Academic Publishers. pp. 27--35.
Cliometric Metatheory II: Criteria Scientists Use in Theory Appraisal and Why It is Rational to Do So.P. Meehl - 2002 - Psychological Reports 91:339--404.
Truthlikeness and Economic Theory.I. Niiniluoto - 2002 - In U. Mäki (ed.), Fact and Fiction in Economics. Cambridge University Press. pp. 214--228.
Twilight of the Perfect Model Model.Paul Teller - 2001 - Erkenntnis 55 (3):393-415.
Refined Verisimilitude.S. D. Zwart - 2001 - Kluwer Academic Publishers.
Verisimilitude.Chris Brink - 2001 - In W. H. Newton-Smith (ed.), A Companion to the Philosophy of Science. Blackwell. pp. 561--563.
Belief Revision and Truthlikeness.I. Niiniluoto - 1999 - In B. Hansson, S. Halld’en, N.-E. Sahlin & W. Rabinowicz (eds.), Internet Festschrift for Peter Gärdenfors. Department of Philosophy, Lund University.