The Junkyard

A post by Fiora Salis.

The problem of how scientists gain knowledge of reality through imagination in scientific models is still largely unresolved. Consider the Lotka-Volterra model of predator-prey dynamics. The model is usually identified with two differential equations interpreted as describing the growth rates of two populations, one prey and one predator, dynamically interacting with each other. To facilitate mathematical treatment, the model makes a number of assumptions, including that predators have infinite appetite, prey have limitless supplies of food, and the environment never changes. These assumptions enable the isolation of certain features of predator-prey interaction (including for example the density of the two populations) not by abstracting away from some particular predators and prey interacting with each other, but by stipulating that some populations having certain features interact in such and such a way. These assumptions, of course, are false (the idealized populations do not exist in reality), but they are not lies either. They are the product of creative uses of imagination that divert from reality to generate a model system as the object of study. They describe two imaginary populations interacting with each other under imaginary conditions. And this enables the generation of certain hypotheses and the assessment of their truth-likeness. The model predicts that the dynamic interaction between predators and prey will show a cyclical relationship in their numbers. Imagination is therefore vital both to the construction and development of the model and to the generation of plausible hypotheses.

A post by Fiora Salis.

Scientific models crucially involve imagination. But what sort of imagination is this? Answering this question is crucial to an understanding of the ways in which scientists construct and develop models in order to learn about reality. Philosophers of science do not offer explicit analyses of imagination but they commonly associate it with mental imagery. Some authors see the imagistic character of imagination as an asset in explaining how scientific models work, but most scientists and philosophers dismiss the imagination as soon as it is linked to mental imagery. I share this scepticism and I offer reasons for it toward the end of this post. But one cannot see the imagination as being crucial to scientific models and also dismiss it because of its allegedly imagistic character. The solution I have offered to this apparent puzzle consists in arguing that the sort of imagination that is really crucial to scientific models is propositional imagination of the make-believe variety (Salis 2016, Salis and Frigg forthcoming). Here I will briefly state the main argument in support of this idea.