The term nomological machine was coined by philosopher Nancy Cartwright. It is the conceptual equivalent of a literal machine. A mathematical model is a nomological machine. And so is a controlled experiment—which may take the form of a literal machine. To be described mathematically at all, a natural system must first be redefined as such a conceptual system. Otherwise, it would not involve clearly defined variables. Deductionism is the belief that all of physical reality can be mapped by such constructs, and even is isomorphic to literal machines such as quantum computers. However, despite the mechanist metaphor, nature is not literally a machine. A controlled experiment is an artificial version of a real situation in nature. Real systems cannot generally be controlled to isolate specific factors of interest, and the number of factors involved is indefinite. A computer simulation is also an artificial version of a natural reality—literally a nomological machine. In that case, deductionism is the belief that all of physical can be simulated by a digital computer, or perhaps by a quantum computer. Extending this to the universe as a whole, and pushed to the extreme, it is the belief that the universe itself is a nomological machine.