The paper deals with the problem of the ontology of political artefacts. A political artefact is a material object that produces certain effects on the social and political environment. The philosophical question I would like to answer is if such an artefact is political because its materiality imposes a social or political norm, or because it simply describes and reproduces certain relations of power. Therefore, I discuss and criticize some of the most relevant theories (technological determinism, social constructivism, Actor-Network-Theory) that deals with the problem of political artefacts and the relation between humans and things. After that, I defend an approach that I define “material contextualism”. In the conclusion, I show why a philosophical theory of the wall, namely a material object that inscribes on the space a relation of power, must be grounded on the material contextualism.