In contrast to mechanism schemas and sketches, some models of mechanisms work not by describing all of the parts, causal interactions, and organizational features, but rather by abstracting away from such potentially obfuscating details (Craver and Darden 2013; Strevens 2008; Levy and Bechtel 2012). In such cases, idealizing assumptions can be introduced to bring the relevant feature of the mechanism most clearly into view: infinite populations, frictionless planes, perfect geometrical shapes are presumed in order to strip the model of detail that does not matter for, or would only obstruct, the intended purposes of model.