Observables

The possibility of testing contradictory statements about the factual world has been suggested but barely discussed in the relevant literature. Here I argue that if we assume that there are contradictory observation sentences, it would be logically impossible to falsify them. Accordingly, the extension of the dialetheist programme into empirical science would be non-advisable, for it would introduce logically unfalsifiable claims.

Bas van Fraassen’s antirealist view of science and its aim, constructive empiricism, notoriously rests upon a distinction between observable and unobservable entities. In order to back his empiricist stance, the Dutch philosopher put forward his own characterization of observability. Nonetheless, he acknowledges that the point of constructive empiricism is not lost if the line is drawn in a somewhat different way from how he draws it. This means that other characterizations of observability can support this antirealist stance, provided they allow (...) for a viable distinction between the observable and the unobservable. The aim of this work, however, is not to propose another characterization of observability that fits constructive empiricism, but to put forward a little amendment to van Fraassen’s own antirealism, to the effect that it can actually be seen as a coherent position, albeit controversial, since its present consistency might be called into question. (shrink)

Popper restricted his definition of falsifiability to consistent theories through what we may call his requirement of consistency. His main argument was that an inconsistent theory does not distinguish the sentences that corroborate it from those that contradict it, for all sentences follow from it. I propose to replace this requirement by the more basic requirement that the classes of potential corroborators and falsifiers of a theory do not overlap. This results not only in an unrestricted definition of falsifiability but (...) also in some inconsistent theories being falsifiable whenever that inconsistency is not located among its observational statements. Although this assumes a restriction of the principle of explosion or ex contradictione sequitur quodlibet (ECQ), it does not depend on any particular system or approach of paraconsistent logic. Finally, I propose to define the class of potential refuters of a theory, which is obtained by subtracting the class of potential corroborators from the class of potential falsifiers. Given that, by definition, the classes of potential refuters and corroborators of a theory do not overlap, it immediately follows that some observationally inconsistent theories are refutable in this sense. This establishes the bases for a new and more general formal theory of falsifiability of scientific factual/empirical theories. (shrink)

Martin Kusch has recently defended Bas van Fraassen’s controversial view on microscopes, according to which these devices are not ‘windows on an invisible world’, but rather ‘image generators’. The two authors also claim that, since in a microscopic detection it is not possible to empirically investigate the geometrical relations between all the elements involved, one is entitled to maintain an agnostic stance about the reality of the entity allegedly represented by the produced image. In this paper I argue that, contrary (...) to what Kusch maintains, this might not be a neutral way to render scientific evidence. Moreover, a constructive empiricist can support a realist interpretation of microscopic images. In fact, constructive empiricism and van Fraassen’s own anti-realism do not necessarily amount to the same thing. (shrink)

In a recent work published in this journal, “Van Fraassen e a inferência da melhor explicação” (2016), Minikoski and Rodrigues da Silva identify four critical lines proposed by Bas van Fraassen against the form of abductive reasoning known as ‘inference to the best explanation’ (IBE). The first one, put forward by the Dutch philosopher in his seminal book The Scientific Image (1980), concerns the distinction between observable and unobservable entities. Minikoski and Rodrigues da Silva consider that the distinction is of (...) no relevance to the scientific practice. For this reason, they address van Fraassen’s allegations against IBE qua justification of the existence of unobservable entities in a couple of pages and prefer focusing on the other lines they identified. The aim of this work is to pour over the analysis that the two authors perform about van Fraassen’s mentioned argument and some realists’ replies, particularly in the section that Minikoski and Rodrigues da Silva devote to this topic. This will allow us to clarify van Fraassen’s vision on scientific practice and on the ‘immersion in the theoretical world-picture’. The importance and the relevance of the distinction between observables and unobservables will also be reaffirmed. (shrink)

In 1985, Alan Musgrave raised a serious objection against the possibility that a constructive empiricist could coherently draw the distinction between observables and unobservables. In his brief response in the same year, Bas van Fraassen claimed that Musgrave’s argument only works within the so-called ‘syntactic view’ of theories, while it loses its force in the context of the ‘semantic view’. But this response was not adequate, or so claimed F. A. Muller, who published two articles in order to extend the (...) epistemology of constructive empiricism. In order to do so, Muller provided a rigorous characterization of observability that requires the use of modal logic. The outcome was a new epistemology for constructive empiricism, which van Fraassen apparently endorsed. As will be shown in this article, however, Muller’s extended epistemology is superfluous. Moreover, and more importantly, Musgrave’s argument seems to be a pseudo-problem. (shrink)

The notion of epistemic community is crucial for the characterization of observability, a cornerstone for Bas van Fraassen’s constructive empiricism. As a matter of fact, observable is, to him, a short for observable-by-us. In this work, it will be shown that the alleged rigidity of the author of The Scientific Image, apparently not very keen to admitting changes in the epistemic community (constituted – according to him – by the human race), is actually an assumption of modesty and good judgment; (...) it means recognizing that scientific enterprise is just a human activity, among many others. (shrink)

Constructive empiricism is a prominent anti-realist position whose aim is to make sense of science. As is well known, it also crucially depends on the distinction between what is observable and what scientific theories postulate but is unobservable to us. Accordingly, adopting an adequate notion of observability is in order, on pain of failing to achieve the goal of grasping science and its aim. Bas van Fraassen, the originator of constructive empiricism, identifies observation with unaided (at least in principle) human (...) perception. So far, though, he has not put forward any convincing argument to support this (unpopular) stand. He did it on the grounds that it is (allegedly) a matter for empirical investigation and not for philosophical analysis. Nonetheless, he seems to have introduced a criterion for observability that is not the result of any scientific research and is not supported by any scientific theory. Countering his own words, he seems to have instead reflected qua philosopher on how an empiricist should interpret the meaning of the verb ‘to observe’. And then tried to defend his point of view by means of metaphors and analogies. But the very same metaphors and analogies van Fraassen put forward could be used to back up the opposite position. Worse, not only does his criterion counter common sense, it does not work either. Perhaps the time has come for van Fraassen to put forward or endorse alternative criteria of observability. (shrink)

In order to defend his controversial claim that observation is unaided perception, Bas van Fraassen, the originator of constructive empiricism, suggested that, for all we know, the images produced by a microscope could be in a situation analogous to that of the rainbows, which are ‘images of nothing’. He added that reflections in the water, rainbows, and the like are ‘public hallucinations’, but it is not clear whether this constitutes an ontological category apart or an empty set. In this paper (...) an argument will be put forward to the effect that rainbows can be thought of as events, that is, as part of a subcategory of entities that van Fraassen has always considered legitimate phenomena. I argue that rainbows are actually not images in the relevant (representational) sense and that there is no need to ontologically inflate the category of entities in order to account for them, which would run counter to the empiricist principle of parsimony. (shrink)

The primacy of the act of observation, one of the hallmarks of empiricism, found new life in the centrality of the distinction, made in Bas van Fraassen's constructive empiricism, between observable and unobservable. As Elliott Sober have pointed out, however, it is not clear what van Fraassen understands by observing an object. Worse, the Dutch philosopher does not seem to consider that a clarification of this point is necessary. This, of course, represents an important lacuna in a position generally considered (...) as the main reference for modern empiricism. My goal is to take up again the counterfactual conditionals characterizing perception that Otávio Bueno presented in 2011 in this journal, and also to consider the observability and the existence criteria proposed by Filip Buekens and Michel Ghins, in order to get to a definition of observation that should give van Fraassen's observability concept the support it actually lacks, but without presenting itself as an ad hoc solution. (shrink)

The concept of observability is of key importance for a consistent defense of Constructive Empiricism. This anti-realist position, originally presented in 1980 by Bas van Fraassen in his book The Scientific Image, crucially depends on the observable/unobservable dichotomy. Nevertheless, the question of what it means to observe has been faced in an unsatisfactory and inadequate manner by van Fraassen and this represents an important lacuna in his philosophical position. The aim of this work is to propose a characterization of the (...) act of observation able to give the necessary support to the ‘rough guide’ of ‘observable’ that can be found in the aforementioned book. Countering van Fraassen’s own statements, that observability is not a matter for philosophy, but for scientific inquiry only, we maintain that any attempt to deal with this subject by the philosophers is legitimate. We will show that van Fraassen ended up doing a philosophical analysis of observation himself, albeit in a fragmentary way. We believe that this question should be dealt with methodically, though, ‘following the rules’ of a ‘proper’ philosophical analysis, as we attempted to do in this work. We will propose a way of conceiving the act of observation, different from van Fraassen’s one, that can help not only to ground the distinction between observable and unobservable, upon which Constructive Empiricism rests, but to get this anti-realist position closer to scientific practice as well, which is one of its desiderata. Without neglecting the philosophical dimension of the issue, though. However, this proposal does not represent an ad hoc ‘solution’ for Constructive Empiricism, but a characterization aspiring to have a universal reach. (shrink)

Discutindo acerca das centenas de detecções de planetas extrassolares, que supostamente aconteceram desde 1989 e que ele considera (incorretamente) como instâncias de observações, Peter Kosso disse, justamente, que segundo os parâmetros de Bas van Fraassen esses objetos celestes seriam observáveis. Ora, tais astros poderiam sem dúvida ser observados diretamente (sem a necessidade de instrumentos), nas condições apropriadas. Mas, acrescenta Kosso, “esse tipo de epistemologia externalista, que permite que a justificação se baseie em informação que não temos a disposição (nós não (...) estamos em condição de ver planetas extrassolares a olho nu [atualmente]), não ajuda a decidir quais particulares afirmações científicas garantem a crença” (Kosso 2006, 225, nota 1). Van Fraassen provavelmente incorre em uma petição de princípio não muito diferente daquelas que ele muitas vezes desmascarou em textos de autores realistas, quando apela para o fato de o objeto detectado ser observável, para atribuir o estatuto de ‘observação’ a uma certa detecção. O ponto é, mais uma vez, entender o que vale como observação, particularmente quando isso envolve o uso de algum instrumento. Endossar aquilo que Otávio Bueno chama de ‘padrão internalista’ parece garantir solidez à qualificação de determinadas ações como observações. Uma das principais consequências dessa adoção é que tal critério, não operando nenhuma distinção relevante entre detecções ‘diretas’ e detecções mediadas por instrumentos, permite que a linha que separa observáveis e inobserváveis seja traçada de maneira diferente de como van Fraassen acredita que deveria ser, abarcando, entre os observáveis, mais (tipos de) entidades do que esse parece estar disposto a admitir. (shrink)

Is there an ontological question relative to van Fraassen’s Constructive Empiricism? It seems so, despite this philosophical position, a reference for contemporary Empiricism, presenting itself as an epistemological thesis. It is, furthermore, a very up-to-date matter, as the Dutch philosopher has recently changed his mind about the possibility for us to observe common optical phenomena as the rainbow. This reveals the necessity for a discussion about the concept of phenomena as used by van Fraassen, as Foss stated more than twenty (...) years ago, but also – and this is an intertwined question – about what ontology is assumed by Constructive Empiricism. (shrink)

According to Bas van Fraassen, a postulated entity which can only be detected by means of some instrument should not be considered observable. In this paper I argue that (1) this is not correct; (2) someone can be a constructive empiricist, adhering to van Fraassen’s famous anti-realist position, even admitting that many entities only detectable with a microscope are observable. The case of the paramecium, a very well-known single-celled organism, is particularly instructive in this respect. I maintain that we actually (...) observe paramecia and not just detect them, contrary to what van Fraassen claims. As a matter of fact, even if we can only perceive these protozoans by using a microscope, we are in condition to know that the relevant counterfactual conditions (like the ones Bueno proposed in 2011) are met. Moreover, paramecia satisfy observability and existence criteria proposed by Buekens (1999) and Ghins (2005). But admitting paramecia and the like among the observables does not threaten Constructive Empiricism, for there will always be a line between observables and unobservables on which van Fraassen’s anti-realism can rest. (shrink)

The problem of the justification of inductive inferences, also known as ‘Hume’s problem’, seems to have lost strength since the early 20th century, following several authors’ denial that induction is the method of science. Van Fraassen went beyond this denial and recently stated that induction does not exist. It is our aim to show that, in order to bring forward a coherent vision of science, in his reconstruction it is the observable (a crucial term for his Constructive Empiricism) that is (...) logically prior to the act of observing and not the other way round. We called this ‘the reverse image of observation’. (shrink)

This article offers a simple technical resolution to the problem of induction, which is to say that general facts are not always inferred from observations of particular facts, but are themselves sometimes defeasibly observed. The article suggests a holistic account of observation that allows for general statements in empirical theories to be interpreted as observation reports, in place of the common but arguably obsolete idea that observations are exclusively particular. Predictions and other particular statements about unobservable facts can then appear (...) as deductive consequences of such general observation statements, rather than inductive consequences of other particular statements. This semantic shift resolves the problem by eliminating induction as a basic form of inference, and folding the justification of general beliefs into the more basic problem of perception. (shrink)

In this paper we investigate the coupling properties of pairs of quadrature observables, showing that, apart from the Weyl relation, they share the same coupling properties as the position-momentum pair. In particular, they are complementary. We determine the marginal observables of a covariant phase space observable with respect to an arbitrary rotated reference frame, and observe that these marginal observables are unsharp quadrature observables. The related distributions constitute the Radon transform of a phase space distribution of the covariant phase space (...) observable. Since the quadrature distributions are the Radon transform of the Wigner function of a state, we also exhibit the relation between the quadrature observables and the tomography observable, and show how to construct the phase space observable from the quadrature observables. Finally, we give a method to measure together with a single measurement scheme any complementary pair of quadrature observables. (shrink)

In this paper we motivate and develop the analytic theory of measurement, in which autonomously specified algebras of quantities (together with the resources of mathematical analysis) are used as a unified mathematical framework for modeling (a) the time-dependent behavior of natural systems, (b) interactions between natural systems and measuring instruments, (c) error and uncertainty in measurement, and (d) the formal propositional language for describing and reasoning about measurement results. We also discuss how a celebrated theorem in analysis, known as Gelfand (...) representation, guarantees that autonomously specified algebras of quantities can be interpreted as algebras of observables on a suitable state space. Such an interpretation is then used to support (i) a realist conception of quantities as objective characteristics of natural systems, and (ii) a realist conception of measurement results (evaluations of quantities) as determined by and descriptive of the states of a target natural system. As a way of motivating the analytic approach to measurement, we begin with a discussion of some serious philosophical and theoretical problems facing the well-known representational theory of measurement. We then explain why we consider the analytic approach, which avoids all these problems, to be far more attractive on both philosophical and theoretical grounds. (shrink)

The Bell–Kochen–Specker contradiction is presented using continuous observables in infinite dimensional Hilbert space. It is shown that the assumption of the existence of putative values for position and momentum observables for one single particle is incompatible with quantum mechanics.

An imprecise measurement of a dynamical variable (such as a spin component) does not, in general, give the value of another dynamical variable (such as a spin component along a slightly different direction). The result of the measurement cannot be interpreted as the value of any observable that has a classical analogue.

A general algebraic system M is considered with two binary operations. The family of all measurable functions with values in the unit interval is a motivating example. A state is a morphism from M to the unit interval, an observable is a morphism from the family of Borel sets to M. A joint distribution of two observables is constructed. It is applied for the construction of the sum of observables and for a representation of conditional probability.

It is not possible to dismiss the atomistic paradigm because the proposed elementary particles are too many (and, hence, it is claimed, they do not provide a simple account of nature) or because it is not possible to observe quarks in an isolated manner. The developments in particle physics have brought about radical changes to our notions of simplicity and observability, and in this paper we elaborate on these changes. It is as a result of these changes that the present (...) situation in elementary particle physics justify us to claim that we have indeed reached a level of explanation where the constituent particles (quarks, leptons, gluons, and intermediate bosons) used for the explanation of the various phenomena considered to be delineating a particular level in the descriptive framework of the physical phenomena and a specific stratum in the organization of nature, can be regarded as elementary. (shrink)

The concept of generalized observable in the scheme of Hilbert quantum mechanics is discussed. We give an example of a possible ambiguity of this notion. The role of interpretation and the strong connection with concrete experimental procedures in the discussion of generalized observables are stressed to explain the above ambiguity.

Common eigenfunctions of nontrivial projectors of x and p are constructed.

Observables on hypergraphs are described by event-valued measures. We first distinguish between finitely additive observables and countably additive ones. We then study the spectrum, compatibility, and functions of observables. Next a relationship between observables and certain functionals on the set of measures M(H) of a hypergraph H is established. We characterize hypergraphs for which every linear functional on M(H) is determined by an observable. We define the concept of an “effect” and show that observables are related to effect-valued measures. Finally, (...) we define “operational” transformations from M(H) to itself and show that they can be described as a certain combination of effects. (shrink)

Two postulates concerning observables on a quantum logic are formulated. By Postulate 1 compatibility of observables is defined by the strong topology on the set of observables. Postulate 2 requires that the range of the sum of observables ought to be contained in the smallestC-closed sublogic generated by their ranges. It is shown that the Hilbert space logicL(H) satisfies the two postulates. A theorem on the connection between joint distributions of types 1 and 2 on the logic satisfying Postulate 2 (...) is proved. (shrink)

In Patterns of Discovery, [1], and Concept of the Positron, [2], the late N. R. Hanson put forward an intersting and, I believe, essentially sound argument to the effect that, necessarily, micro-entities are "unpicturable." Hanson's claim is centrally a claim about microreduction, but his use of the term 'unpicturable' may be misleading, generating critiques which overplay its implications and its importance. A. M. Paul, in a recent article, [4], has taken Hanson to task in this regard, claiming that the notion (...) of picturability is so cloudy as to render Hanson's whole enterprise unconvincing. In what follows I shall critically discuss Hanson's argument and Paul's analysis and attempt to state a version of it capable of meeting Paul's objections. I will claim that Hanson's use of the term 'unpicturable' may be, at worst, infelicitous, and that his thesis concerning micro- or property-reduction remains unaffected by questions concerning what we can or cannot picture. (shrink)