A computer does not make a world exist, it describes it
The mathematical universe hypothesis and simulation (Tegmark)
A simulated universe exists as truly as ours: "simulated" does not mean "less real", only "specified by a computer".
Running the computer does not change whether the described world exists: simulated or not, it exists the same way.
"A computer does not make a world exist, it describes it" is an argument by Max Tegmark (Tegmark, "The Mathematical Universe", 2008, 2008) on the question "Is the world real?" (answer: virtual is real too). Its claim: A simulated universe exists as truly as ours: "simulated" does not mean "less real", only "specified by a computer". According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 2 objections, 0 of them with a documented reply, and the original text behind each premise, checked word for word.
The cosmologist Max Tegmark defends a bold idea: our physical world is not described by mathematics, it is a mathematical structure, that is, abstract objects and the relations among them. From this he draws a consequence about simulations. If one simulated a universe on a computer, that universe would also be a mathematical structure, and it would exist already, before anyone computes it. The computer's role would not be to compute the universe's history but to specify it. Whether the computer runs or not makes no difference to whether that universe exists. A caveat: everything rests on the mathematical universe hypothesis, which Tegmark presents as following from the existence of a reality outside us, and which is widely disputed.
click a premise to reject it
Without the implicit premise: Without P4 one can imagine that mathematical structures exist "in general" without that being enough to make a world one lives in: an equation exists, but nobody lives in it. The argument alone would not say the described world is real.
Objections
2Each objection is a conversation: click to see who replies and where the debate stands.
SSabine Hossenfelder 2007 · attacks premise 1Hossenfelder, a physicist, says mathematics describes reality but is not reality. One can think of and describe an electron's wavefunction even if the electron does not exist, and that does not make the electron real. She sees a difference that Tegmark's hypothesis erases.
no reply
Hossenfelder, a physicist, says mathematics describes reality but is not reality. One can think of and describe an electron's wavefunction even if the electron does not exist, and that does not make the electron real. She sees a difference that Tegmark's hypothesis erases.
GGordon McCabe 2005 · attacks premise 2McCabe argues that a digital simulation has no objective link to the system it simulates: it exists only as a physical process in the computer's parts. So nobody can live "inside" a digital simulation, and there is no simulated world that could be called real.
no reply
McCabe argues that a digital simulation has no objective link to the system it simulates: it exists only as a physical process in the computer's parts. So nobody can live "inside" a digital simulation, and there is no simulated world that could be called real.