Despite being one of the most commonly used normative concepts in urban design, coherence still lacks a firm morphological definition. Without an explicit specification of its spatial attributes, coherence remains a vague and subjective notion of design implicitly referred to as one of the basic properties of good urban form. As a contribution to the link between urban design and morphology, this paper renders the normative concept objectively in terms of a set of quantifiable morphological indicators. Spatial proximity and consistency are suggested as the two key indicators for measuring the coherence of urban fabric. Based on the computational theory of coherence, originally put forward by Thagard, an analytical model is suggested to quantify) the morphological coherence of actual urban fabrics. In this framework, three planned neighbourhoods in Rotterdam, the Netherlands are analysed to illustrate the changing nature of morphological coherence through different fashions of urbanism initiated in different periods of time.