QuestionsWhy is there something rather than nothing?A universe can arise by quantum tunnelling from a state with no space and no time
Why is there something rather than nothing?Physics answers

A universe can arise by quantum tunnelling from a state with no space and no time

Creation of universes from nothing (Vilenkin)

Alexander Vilenkin born 1949A cosmologist who proposed in 1982 that a universe could arise by quantum tunnelling from "nothing".
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What it claims

A universe can arise from nothing by a process that quantum physics describes, with no pre-existing matter or spacetime.

Why

In quantum physics, a small universe can arise by tunnelling from a state with no space or time, then grow by inflation.

The same idea through history
Alexander Vilenkin1982Vilenkin proposes a model where the universe is created by quantum tunnelling "from literally nothing" into a de Sitter space, with no initial singularity and no initial condition.
Stephen Hawking2010Hawking and Mlodinow argue that gravity lets the universe create itself from nothing.Lawrence M. Krauss2012Krauss presents to the general public the idea that a universe can arise from the quantum vacuum.
In short

"A universe can arise by quantum tunnelling from a state with no space and no time" is an argument by Alexander Vilenkin (Creation of universes from nothing, 1982, 1982) on the question "Why is there something rather than nothing?" (answer: physics answers). Its claim: A universe can arise from nothing by a process that quantum physics describes, with no pre-existing matter or spacetime. 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, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Creation of universes from nothing, 1982
Valid with an implicit premise

In 1982 the physicist Alexander Vilenkin published a paper titled "Creation of universes from nothing". It proposes a model of quantum cosmology: the universe is born by tunnelling, like a particle crossing a barrier, from a state he calls "nothing". In later texts Vilenkin specifies this word: a state with no classical space and time. After the birth the universe goes through a phase of inflation. The argument does not say there is "nothing at all" before: it says quantum physics describes a beginning with no prior matter or time. A caveat: Vilenkin himself notes that the universe's wave function depends on boundary conditions that must be postulated as a physical law, which one hopes will one day be derived from a fundamental theory.

P1To understand the beginning of the universe, we can treat it quantum-mechanically and describe it by a wave function rather than a classical spacetime.
P2In this description, a small closed universe can arise spontaneously, by tunnelling, from a state with no classical space and time.
P3Once born, this universe goes through a phase of inflation that leads to today's universe. The model needs neither an initial singularity nor an initial condition.
P4 · implicit premiseA state with no classical space and time is indeed a "nothing" in the sense relevant to the question: there is no pre-existing matter, place or duration to be explained.
Therefore a universe can arise from nothing by a process that quantum physics describes, with no pre-existing matter or spacetime.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the computer finds a case where the universe is born by tunnelling from a state with no classical spacetime, but where that state still contains laws and fields: that is not "nothing".
Valid with P4. The hidden premise is the one under discussion: calling "nothing" a state with no classical spacetime is a choice of definition. If "nothing" also means without laws or fields, the conclusion does not follow. This is not a logical error of the argument, but the heart of the disagreement.
Analogy. A particle crossing a barrier it does not have enough energy to climb: in quantum physics this happens with some probability. Vilenkin applies the idea to the whole universe. The image is ours.

Objections

2

Each objection is a conversation: click to see who replies and where the debate stands.

D
David Albert 2012 · attacks premise 4

Albert, a philosopher of physics, says in reply to another book (Krauss's) that the true equivalent of "nothing" in quantum field theories would be the absence of the fields themselves. A state with no classical spacetime, but described by a wave function and laws, is still "something".

Vilenkin replies
Alexander Vilenkin 2002 · Vilenkin's clarification (2002)
Vilenkin specifies what he means by "nothing": a state with no classical space and time. This text predates Albert's criticism and does not answer it: it shows that Vilenkin does not use the word to mean an absence of everything.
The debate goes on (our summary) The disagreement is thus verbal at first: what remains is whether the laws and the wave function also need explaining, which Vilenkin leaves open (our summary).
Where the debate stands (our summary)The disagreement is about the meaning of the word "nothing". If it means the absence of classical space and time, the model is an example; if it means the absence of everything, laws included, it is not. This definitional split is unsettled (our summary).
Gottfried Wilhelm Leibniz 1714 · attacks the conclusion

The sufficient reason cannot be found in the sequence of contingent things. Even if the starting state is called "nothing", one must say why these laws and this wave function exist rather than others or none. This is not a reply by Leibniz to Vilenkin, which never took place, but the modern form of his principle of reason.

Vilenkin replies
see the argument
Alexander Vilenkin 2002 · Vilenkin on the laws (2002)
Vilenkin acknowledges that the boundary conditions of the universe's wave function must be postulated as an independent physical law, debated for nearly twenty years, and says he hopes it will one day be derived from the fundamental theory.
Where the debate stands (our summary)Open point: physics describes how a universe can be born from a state without spacetime, but it assumes laws. Whether the existence of these laws calls for an explanation is a question both camps still consider open (our summary).