Inflation

Exponential expansion of the multiverse driven by the repulsive gravity of the false (high energy) vacuum; inflation is likely to be eternal, i.e., once started, it will never end.

Multiverse (megaverse, master universe)

The entire fabric of reality that consists of eternally inflating false vacuum with an infinite number of decaying small decaying regions giving rise to universes.

Universe (island universe, pocket universe, bubble universe)

Part of the multiverse that expands from a Big Bang event resulting from a decay of a region of false vacuum into low energy (true) vacuum. A universe is infinite from the point of view of an internal observer but finite to an imaginary external observer.

Observable (
O
) region

A finite region within a universe that can be observed from any given point, i.e., the interior of the past light cone of the given point; our Oregion contains ~10^{20} stars.

Big Bang

In the traditional 20^{th} century cosmology, expansion of the universe from a singularity; the nature of the "bang" has never been elucidated. In the eternal inflation cosmology, Big Bang corresponds to the end of inflation in the given region of the multiverse as a result of false vacuum decay and the formation of a universe in the form of an expanding bubble of lowenergy (true) vacuum.

Macroscopic (coarsegrained) history

Any combination of physical events permitted by the laws of physics, characterized to the limit of quantum uncertainty and occurring in an Oregion within a finite time; it has been shown that the number of all possible macroscopic histories is finite, although vast. Hence even within a single universe, each history is repeated an infinite number of times.

Probability/chance/randomness

Textbooks define probability as the limit to which frequency of a specific outcome tends when the number of trials tends to infinity. In an infinite universe (and, obviously, in the multiverse) with a finite number of histories, the infinite number of trials is realized, hence probability equals frequency. The probability of any permissible history including origin of life, then, is P = 1. However, the probability p of observing any particular history in a given Oregion lies in the interval between 0 and 1 as in the textbook definition of probability and can be extremely small for a vast number of histories including the origin of life. Thus, the notions of chance and randomness apply only to finite regions of a universe, whereas in an infinite universe as a whole, the realization of all permitted histories is a necessity.

Anthropic principle/anthropic selection/anthropic reasoning

The notion that the history of our world (our Oregion, our galaxy, our solar system etc) prior to the onset of biological evolution does not depend on any special "mechanism" but was, simply, "selected" from the finite ensemble of all histories that are guaranteed to realize in an infinite universe, by virtue of being conducive to the emergence of complex life. Anthropic selection is an epistemological not an ontological principle, and should not be misconstrued for any kind of active process. This is a formulation of the "weak" anthropic principle adopted for the context of this paper. The "strong" anthropic principle is the notion that the emergence of consciousness, somehow, is a goal of the cosmic history. This is a teleological, nonscientific concept.
