 Early in the 20th century, the unity of consciousness almost disappeared from the research agenda. Logical atomism in philosophy and behaviourism in psychology had little to say about the notion. Logical atomism focussed on the atomic elements of cognition (sense data, simple propositional judgments, protocol sentences, etc.), rather than on how these elements are tied together to form a mind. Behaviourism urged that we focus on behaviour, the mind being either a myth or at least something that we cannot and do not need to study in a science of the human person. 