Intervening mechanism evaluation

‘The intervening mechanism evaluation approach assesses whether the causal assumptions underlying a program are functioning as stakeholders had projected (Chen, 1990). […] It is not always labeled in the same way by those who apply it. Some evaluators have referred to it as “theory of change evaluation” (Connell, Kubisch, Schorr, & Weiss, 1995) or “theory-based evaluation” (Rogers, Hasci, Petrosino, & Huebner, 2000; Weiss, 1997).’

Chen, H. T. (2015, p. 312). Practical Program Evaluation: Theory-Driven Evaluation and the Integrated Evaluation Perspective. SAGE Publications Ltd.

“A mechanism is one of the processes in a concrete system that makes it what it is”

What a lovely paper! Here are some excerpts:

‘A mechanism is one of the processes in a concrete system that makes it what it is—for example, metabolism in cells, interneuronal connections in brains, work in factories and offices, research in laboratories, and litigation in courts of law. Because mechanisms are largely or totally imperceptible, they must be conjectured. Once hypothesized they help explain, because a deep scientific explanation is an answer to a question of the form, “How does it work, that is, what makes it tick—what are its mechanisms?”’ (p. 182; abstract)

‘Consider the well-known law-statement, “Taking ‘Ecstasy’ causes euphoria,” which makes no reference to any mechanisms. This statement can be analyzed as the conjunction of the following two well-corroborated mechanistic hypotheses: “Taking ‘Ecstasy’ causes serotonin excess,” and “Serotonin excess causes euphoria.” These two together explain the initial statement. (Why serotonin causes euphoria is of course a separate question that cries for a different mechanism.)’ (p. 198)

‘How do we go about conjecturing mechanisms? The same way as in framing any other hypotheses: with imagination both stimulated and constrained by data, well-weathered hypotheses, and mathematical concepts such as those of number, function, and equation. […] There is no method, let alone a logic, for conjecturing mechanisms. […] One reason is that, typically, mechanisms are unobservable, and therefore their description is bound to contain concepts that do not occur in empirical data.’ (p. 200)

‘Even the operations of a corner store are only partly overt. For instance, the grocer does not know, and does not ordinarily care to find out, why a customer buys breakfast cereal of one kind rather than another. However, if he cares he can make inquiries or guesses—for instance, that children are likely to be sold on packaging. That is, the grocer may make up what is called a “theory of mind,” a hypothesis concerning the mental processes that end up at the cash register.’ (p. 201)

Bunge, M. (2004). How Does It Work?: The Search for Explanatory Mechanisms. Philosophy of the Social Sciences, 34(2), 182–210.