After a decade of intense debate about mechanisms, there is still no consensus characterization. In this paper we argue for a characterization that applies widely to mechanisms across the sciences. We examine and defend our disagreements with the major current contenders for characterizations of mechanisms. Ultimately, we indicate that the major contenders can all sign up to our characterization.

The concept of mechanism is analyzed in terms of entities and activities, organized such that they are productive of regular changes. Examples show how mechanisms work in neurobiology and molecular biology. Thinking in terms of mechanisms provides a new framework for addressing many traditional philosophical issues: causality, laws, explanation, reduction, and scientific change.

Explanations in the life sciences frequently involve presenting a model of the mechanism taken to be responsible for a given phenomenon. Such explanations depart in numerous ways from nomological explanations commonly presented in philosophy of science. This paper focuses on three sorts of differences. First, scientists who develop mechanistic explanations are not limited to linguistic representations and logical inference; they frequently employ diagrams to characterize mechanisms and simulations to reason about them. Thus, the epistemic resources for presenting mechanistic explanations are (...) considerably richer than those suggested by a nomological framework. Second, the fact that mechanisms involve organized systems of component parts and operations provides direction to both the discovery and testing of mechanistic explanations. Finally, models of mechanisms are developed for specific exemplars and are not represented in terms of universally quantified statements. Generalization involves investigating both the similarity of new exemplars to those already studied and the variations between them. (shrink)

Discovery proceeds in stages of construction, evaluation, and revision. Each of these stages is constrained by what is known or conjectured about what is being discovered. A new characterization of mechanism aids in specifying what is to be discovered when a mechanism is sought. Guidance in discovering mechanisms may be provided by the reasoning strategies of schema instantiation, modular subassembly, and forward/backward chaining. Examples are found in mechanisms in molecular biology, biochemistry, immunology, and evolutionary biology.

During the mid-18th century, when electricity was coming into its own, natural philosophers began to entertain the possibility that electricity is the mysterious nerve force. Their attention was first drawn to several species of strongly electric fish, namely torpedoes, a type of African catfish, and a South American "eels." This was because their effects felt like those of discharging Leyden jars and could be transmitted along known conductors of electricity. Moreover, their actions could not be adequately explained by popular mechanical (...) theories. Many of the early documents supportive of the hypothesis of animal electricity were associated with the Dutch colonies in South America. This article presents and examines those documents, and shows how Dutch scientists on both sides of the Atlantic conducted experiments and communicated with each other in the 1750s and 1760s. It reveals the important roles played by inquisitive physicians and lovers of nature in South America, and by natural philosophers and collectors of exotic specimens in the Netherlands—learned men who began to make a credible case for animal electricity in some exciting places at a pivotal moment in time. (shrink)

During the mid-18th century, when electricity was coming into its own, natural philosophers began to entertain the possibility that electricity is the mysterious nerve force. Their attention was first drawn to several species of strongly electric fish, namely torpedoes, a type of African catfish, and a South American "eels." This was because their effects felt like those of discharging Leyden jars and could be transmitted along known conductors of electricity. Moreover, their actions could not be adequately explained by popular mechanical (...) theories. Many of the early documents supportive of the hypothesis of animal electricity were associated with the Dutch colonies in South America. This article presents and examines those documents, and shows how Dutch scientists on both sides of the Atlantic conducted experiments and communicated with each other in the 1750s and 1760s. It reveals the important roles played by inquisitive physicians and lovers of nature in South America, and by natural philosophers and collectors of exotic specimens in the Netherlands—learned men who began to make a credible case for animal electricity in some exciting places at a pivotal moment in time. (shrink)

Discovery proceeds in stages of construction, evaluation, and revision. Each of these stages is constrained by what is known or conjectured about what is being discovered. A new characterization of mechanism aids in specifying what is to be discovered when a mechanism is sought. Guidance in discovering mechanisms may be provided by the reasoning strategies of schema instantiation, modular subassembly, and forward/backward chaining. Examples are found in mechanisms in molecular biology, biochemistry, immunology, and evolutionary biology.

Semmelweis’s discovery of the cause of puerperal fever around the middle of the 19th century counts among the paradigm cases of scientific discovery. For several decades, philosophers of science have used the episode to illustrate, appraise and compare views of proper scientific methodology.Here I argue that the episode can be profitably reexamined in light of two cognate notions: causal reasoning and mechanisms. Semmelweis used several causal reasoning strategies both to support his own and to reject competing hypotheses. However, these strategies (...) have gone unappreciated in the existing literature. I show that a causal reasoning approach makes sense of the multitude of tables in Semmelweis’s main text, which in later editions were often abridged because they appeared redundant.Moreover, the existing literature tends to focus on Semmelweis’s clinical intervention and on the extent to which it alone confirms his theoretical conclusions. This neglects Semmelweis’s efforts to show by animal experiments that his clinical results are in agreement with a demonstrable mechanism of puerperal fever pathogenesis. I argue that the full evidential force of Semmelweis’s argument can only be appreciated if both his clinical and his laboratory investigations are taken into account. (shrink)