Abstract

The concept of a digital twin comes from engineering.1 It refers to a digital model of an artefact in the real world, which takes data about the artefact itself, data about other such artefacts, among other things, as inputs. The idea is that the maintenance of artefacts—such as jet engines—can be vastly improved if we work with digital twins that simulate actual objects. Similarly, personalised medicine might benefit from the digital modelling of body parts or even whole human bodies. A medical digital twin could use data about the patient, more general population data, and other inputs to generate predictions about the patient. This could lead to highly personalised interventions and nuanced judgments about the patient’s health. Matthias Braun2 discusses this intriguing prospect, asking how we should think about the way(s) in which a digital twin could represent a patient. I will respond to Braun’s striking suggestion that we can regard a digital twin as an extension of the patient’s body. Notably, Braun does not compare his just-mentioned idea with the extended mind thesis popularised by Andy Clark and David Chalmers.3 But I am sure many readers will be reminded of the extended mind thesis. Accordingly, I will consider this comparison. I cannot discuss this comparison in detail, nor fully evaluate Braun’s suggestion. But I can say something about how we might approach this comparison, and provide some …