This paper introduces the general features of Senso Comune, an open knowledge base for the Italian language, focusing on the interplay of lexical and ontological knowledge, and outlining our approach to conceptual knowledge elicitation. Senso Comune consists of a machine-readable lexicon constrained by an ontological infrastructure. The idea at the basis of Senso Comune is that natural languages exist in use, and they belong to their users. In the line of Saussure's linguistics, natural languages are seen as a social product and their main strength relies on the users consensus. At the same time, language has specific goals: i.e. referring to entities that belong to the users world (be it physical or not) and that are made up in social environments where expressions are produced and understood. This usage leverages the creativity of those who produce words and try to understand them. This is the reason why ontology, i.e. a shared conceptualization of the world, can be regarded to as the soil on which the speakers' consensus may be rooted. Some final remarks concerning future work and applications are also given.