Many mechanists, following Simon (1996 [1962]), emphasize that biological systems are hierarchically organized into near-decomposable structures: mechanisms within mechanisms, within mechanism. Using the parable of Tempus and Hora, Simon (1962) argued that a watchmaker who builds hierarchically decomposable watches (Tempus) will make more watches than one who builds holistic watches (Hora). This parable led Simon to the conclusion that evolved structures are more likely to be nearly decomposable into hierarchically organized, more or less stable structures and sub-structures. Some have objected that the story is misleading because evolution does not construct organisms from scratch, piece by piece (Bechtel 2009b). Steel (2008), building on the work of others (Schlosser and Wagner 2004), therefore attempts to reconstruct this argument as a way of showing that evolved systems are more likely to be modular: systems made of independently manipulable parts can quarantine the effects of changes to specific parts, giving them added flexibility to make local changes without causing catastrophic side-effects.