This paper focuses on nineteenth-century theories according to which intellectual disabilities find expression in physical impairment. Such theories became widespread in Switzerland due to the growing interest in a condition then called ‘cretinism’ – a specific form of ‘idiocy’ in the course of which mental and physical disintegration went hand in hand. The first institution for ‘cretinic’ children initially achieved considerable fame. However, it eventually failed completely, leading to a loss of interest in ‘cretinism’. Interestingly, the specific body–mind connection that was associated with ‘cretinism’ did not vanish; instead, it became important in the context of another intellectual disability that gained attention after the mid-nineteenth century: ‘idiocy’. Physical aspects became the main criteria for identifying ‘idiotic’ children in order to allocate them to special educational measures. The paper argues that the connection of an ‘abnormal’ mind to an impaired body allowed for the popularisation of knowledge regarding ‘idiotic’ children.