This is a vital point in any multiple universe, or multiverse, model.
It is neither a universe pure and simple nor a multiverse pure and simple.
1895, William James's coinage, an alternative to universe meant to convey absence of order and unity.
But those times are past; and we of the nineteenth century, with our evolutionary theories and our mechanical philosophies, already know nature too impartially and too well to worship unreservedly any god of whose character she can be an adequate expression. Truly all we know of good and beauty proceeds from nature, but none the less so all we know of evil. Visible nature is all plasticity and indifference, a moral multiverse, as one might call it, and not a moral universe. [William James, "Is Life Worth Living?" address to the Young Men's Christian Association of Harvard University, May 1895]