  Some philosophers have put this distinction to work in arguments about the philosophical novelty of simulation. We first raised this issue in section 4.1, where Frigg and Reiss argued that simulation could have no epistemologically novel features, since it contained two distinct components: a component that is identical to the epistemology of ordinary modeling, and a component that is entirely mathematical. “We should distinguish two different notions of reliability here, answering two different questions. First, are the solutions that the computer provides close enough to the actual (but unavailable) solutions to be useful?…this is a purely mathematical question and falls within the class of problems we have just mentioned. So, there is nothing new here from a philosophical point of view and the question is indeed one of number crunching. Second, do the computational models that are the basis of the simulations represent the target system correctly? That is, are the simulation results externally valid? This is a serious question, but one that is independent of the ﬁrst problem, and one that equally arises in connection with models that do not involve intractable mathematics and ordinary experiments” (Frigg and Reiss 2009).