Philosophers of science have had little to say about 'middle-range theory' although much of what is done in science and of what drives its successes falls under that label. These lectures aim to spark an interest in the topic and to lay groundwork for further research on it. 'Middle' in 'middle range' is with respect to the level both of abstraction and generality. Much middle-range theory is about things that come under the label 'mechanism'. The lectures explore three different kinds of mechanism: structural mechanisms or underlying systems that afford causal pathways; causal-chain mechanisms that are represented in what in policy contexts are called 'theories of change' and for which I give an extended account following the causal process theory of Wesley Salmon; and middle-range-law mechanisms like those discussed by Jon Elster, which I claim are – and rightly are – rampant throughout the social sciences. The theory of the democratic peace, that democracies do not go to war with democracies, serves as a running example. The discussions build up to the start of, first, an argument that reliability in social (and natural) science depends not so much on evidence than it does on the support of a virtuous tangle of practices (without which there couldn't even be evidence), and second, a defence of a community-practice centred instrumentalist understanding of many of the central basic principles that we use (often successfully) in social (and in natural) science for explanation, prediction and evaluation.
Cartwright, N. (2020). Lullius Lectures 2018: Mid-level theory: Without it what could anyone do?. THEORIA. An International Journal for Theory, History and Foundations of Science, 35(3), 269-323. https://doi.org/10.1387/theoria.21479