Why is there anything at all?

Measurements of the cosmic microwave background and of light-element abundances constrain conditions in the first minutes with real precision. Known particle physics carries the description back to a small fraction of a second. Earlier than that, what the universe contained depends on physics beyond the Standard Model, which has not been established, and inflation, the leading account of its initial conditions, is still a proposal.

Empty space in quantum field theory is not empty: it is a particular state of the fields, and the fields carry energy from which particles can be created. Physicists’ accounts of the universe emerging “from nothing”, Lawrence Krauss’s among them, begin from that state. Krauss defends the change of subject: science often makes progress by changing what its words mean. David Albert replies that a vacuum is a particular arrangement of physical stuff, not nothing.

A closely related and far more tractable version of the question: the observable universe is made of matter, with very little antimatter, but the known laws are almost symmetric between them. The asymmetry is measured; its cause is an active research problem.

Principles of sufficient reason (the idea that everything must have an explanation) have been argued over for centuries. If the principle holds and the universe is contingent, it needs an explanation outside itself. If it does not, a brute fact is permitted. Neither position has been established, and much of the debate turns on which of them is the default.

Some philosophers argue that an empty world, with no concrete thing in it at all, is not a genuine possibility, so there is no alternative to there being something. Others follow Thomas Baldwin’s subtraction argument: take away the objects of a finite world one at a time, and the last removal leaves nothing. The argument is live.

Suppose the universe emerged from a quantum process. That process obeyed rules. Where the rules came from is the same question in different clothing. Any answer that begins from something that exists has this shape, which is why some philosophers conclude the question cannot be answered.

Several physical constants appear to sit in narrow ranges compatible with complex structure. Whether they could have taken other values, and whether that fact requires explanation, is disputed at a fundamental level, partly because we have no theory that predicts them and no other universes to compare against.

Existence may simply be the case, with no further explanation available. Bertrand Russell held that the universe is “just there, and that’s all”. The position is compatible with everything currently known. Alexander Pruss answers that claiming a brute fact “should be a last resort”, because it would undercut the practice of science; John Mackie, that science would work just as well starting from brute facts.

In most current models, inflation is eternal, producing causally separate bubble universes whose local physics could differ from one to the next; string theory, which appears to allow an enormous number of vacua, would supply the differences. This would explain apparent fine-tuning through selection rather than design. It does not explain why the generating framework exists, and its testability is contested.

A causal answer to why there is something rather than nothing would begin by naming something that already exists. Read as widely as the question demands, there is nothing left to name. One reading of that is not that the answer is hidden but that the question is malformed: it asks of everything what can only be asked of the things inside it, and quietly assumes a vantage point that does not exist.