Johannes Persson

Researchers often aim to make correct inferences both about that which is actually studied and about what the results generalize to. The language of internal and external validity is not used by everyone, but many of us would agree that intuitively the distinction makes a lot of sense. Two claims are commonly made with respect to internal and external validity. The first is that internal validity is prior to external validity since there is nothing to generalize if the findings obtained in, for instance, the experimental setting do not hold. The first claim is explicit in many writings. See for instance Francisco Guala’s influential book The methodology of experimental economics. And it is often implicitly relied on. The second claim is that researchers have to make a trade-off between internal and external validity. When one is increased, the other will decrease. The second claim was made already from the start by D.T Campbell in his classic Factors relevant to the validity of experiments in social settings. There is a certain tension between the first and the second claim. It has been argued before that it might be difficult to combine them. We intend to make the stronger point that both claims are misconstrued. Our hypothesis is that the relationship between internal and external validity has to be re-conceptualized, and we will briefly indicate how

This paper is an attempt to further our understanding of mechanisms conceived of as ontologically separable from laws. What opportunities are there for a mechanistic perspective to be independent of, or even more fundamental than, a law perspective? Advocates of the mechanistic view often play with the possibility of internal and external reliability, or with the paralleling possibilities of enforcing, counteracting, redirecting, etc., the mechanisms’ power to produce To further this discussion I adopt a trope ontology. It is independent of the notion of law, and can easily be adapted to account for such characteristics of mechanisms. The idea of tropes as mechanisms is worked out in some detail. According to the resulting picture, there is still an opportunity to link mechanisms and laws. But while the predominant law view conceives of mechanistic approaches as special kinds of law accounts, this study indicates that the converse may be true. Law accounts are special cases of mechanistic accounts, and they work only in those worlds where the mechanisms are of the right kind.

Jon Elster worries about the explanatory power of the social sciences. His main concern is that they have so few well-established laws. Elster develops an interesting substitute: a special kind of mechanism designed to fill the explanatory gap between laws and mere description. However, his mechanisms suffer from a characteristic problem that I will explore in this article. As our causal knowledge of a specific problem grows we might come to know too much to make use of an Elsterian mechanism but still lack a law. We might then find ourselves in the paradoxical position of knowing more relevant causal truths about the phenomenon we are interested in than we did before, but being able to explain less. If this possibility is realized in social science settings, as I argue it might well be, Elster?s mechanistic account is threatened. Moreover, even if the possibility is rarely realized in that way, it raises, simply as a possibility, a conceptual problem with Elster?s mechanistic framework

Semmelweis’s work predates the discovery of the power of randomization in medicine by almost a century. Although Semmelweis would not have consciously used a randomized controlled trial (RCT), some features of his material—the allocation of patients to the first and second clinics—did involve what was in fact a randomization, though this was not realised at the time. This article begins by explaining why Semmelweis’s methodology, nevertheless, did not amount to the use of a RCT. It then shows why it is descriptively and normatively interesting to compare what he did with the modern approach using RCTs. The argumentation centres on causal inferences and the contrast between Semmelweis’s causal concept and that deployed by many advocates of RCTs. It is argued that Semmelweis’s approach has implications for matters of explanation and medical practice.

Sometimes instances of perceived causation turn out to lack causal relata. The reasons may vary. Causation may display itself as prevention, or as omission, and in some cases causation occurs within such complex environments that few of the things we associate with causes and effects are true of them, etc. But even then, there may be causal explanations to be had. This suggests that the explanatory power of causal reports have other sources than the relation between cause and effect. In this paper it is argued that the causal mechanisms we allude to in explanations have relevant determinables other than the traditionally acknowledged ones. The traditional but in this aspect mistaken view of causation is to be blamed. Discernability, complexity of manifestation, originality, and even stability have often been overlooked. We know, that, in fact, heat is a constant attendant of flame; but what is the connexion between them, we have no room so much as to conjecture or imagine. (Hume 1777, VII. 2, 64).

Isaac Levi is more interested in inquiry and how it progresses than he is in metaphysics. Questions concerning the role of disposition predicates in inquiry are more central to him than those concerning the nature and reality of dispositions. It has not stopped him from giving me and others very useful metaphysical advice. Currently, where empirical metaphysics is in vogue, there is every reason to see whether the two forms of philosophical interest might interlock substantially. Levi has stimulating ideas indeed on the two forms of philosophical interest, and has recently summarized them in the slogan: “The reality of dispositions is a work in progress”. We can learn much about what kinds of dispositions are acceptable from tracing and comparing the histories of successful and less successful disposition predicates in scientific inquiry. Levi explores one route along which dispositions become real. His idea is that the introduction of dispositions facilitates covering law explanation by increasing the number of laws. The successful disposition predicate eventually becomes integrated in scientific theory, much like an ordinary theoretical term, whereas the unsuccessful does not. My impression is that Levi thinks that this is the only way a disposition can become real. To evaluate this claim, an alternative course suggested by Jon Elster is introduced. I then try to bring out the differences between Levi's and Elster's views on dispositions, partly by suggesting that they resemble two aspects of full explanations discussed by Wesley Salmon. But more about that below

The possibility of apparently negative causation has been discussed in a number of recent works on causation, but the discussion has suffered from beingscattered. In this paper, the problem of apparently negative causation and its attemptedsolutions are examined in more detail. I discuss and discard three attempts that have beensuggested in the literature. My conclusion is negative: Negative causation shows that thetraditional cause & effect view is inadequate. A more unified causal perspective is needed.

According to Jon Elster, mechanisms are frequently occurring and easily recognizable causal patterns that are triggered under generally unknown conditions or with indeterminate consequences. In the absence of laws, moreover, mechanisms provide explanations. In this paper I argue that Elster’s view has difficulties with progressing knowledge. Normally, filling in the causal picture without revising it should not threaten one’s explanation. But this seems to be Elster’s case. The critique is constructive in the sense that it is built up from a discussion of a mechanism that might explain ‘unwarranted’ risk taking in connection with swimming—a mechanism that is mirrored in the proverb: The best swimmers drown

Background Positivism is sometimes rejected for the wrong reasons. Influential textbooks on nursing research and in other disciplines tend to reinforce the misconceptions underlying these rejections. This is problematic, since it provides students of these disciplines with a poor basis for making epistemological and methodological decisions. It is particularly common for positivist views on reality and causation to be obscured. Objectives and design The first part of this discussion paper identifies and explains the misconceptions about positivism as they appear in two influential textbooks. The second part pinpoints five mistakes these misconceptions easily result in when the researcher adopts an epistemological and methodological standpoint. What is already known about the topic? There are several impeccable descriptions of positivism in nursing research literature; but a relatively large number of inaccurate or confused views of positivism appear in the nursing research literature as well. Mistakes of the kind identified in this paper have been noted before—for instance, in Shadish. What this paper adds: This paper provides a detailed analysis of two particularly common and influential misconceptions about positivism. It traces the historical roots of these misconceptions and characterizes them more carefully than many earlier attempts have done. The paper shows how and why these misconceptions affect epistemological and methodological decisions negatively, regardless of one’s interest in positivism