I take Eliezer’s position on MWI to be pretty well expressed by this quote from David Wallace:
[...] there is no quantum measurement problem.
I do not mean by this that the apparent paradoxes of quantum mechanics arise because we fail to recognize ‘that quantum theory does not represent physical reality’ (Fuchs and Peres 2000a). Quantum theory describes reality just fine, like any other scientific theory worth taking seriously: describing (and explaining) reality is what the scientific enterprise is about...
What I mean is that there is actually no conflict between the dynamics and ontology of (unitary) quantum theory and our empirical observations. We thought there was originally, because the theory is subtle, complicated and highly unintutive, and because our early attempts to understand it and to relate it to empirical data promote high-level concepts like ‘observation’ and ‘measurement’ to the level of basic posits and confused the issue.
The central case for Everettianism is that it is just plain old quantum mechanics, approached with the default realist perspective that most of us have no problem adopting for practically every other physical theory.* Every other “interpretation” out there adds on extra posits—either ontological posits or epistemological posits that one doesn’t usually hear when talking about other theories—in order to solve a problem that doesn’t actually exist, the so-called “measurement problem”. So it’s not just that MWI is simpler than the other theories; it’s that the sole motivation for the added complexity in other theories—the supposed inadequacy of bare quantum theory to account for our observations—turns out to be bunk.
Suppose someone argued that the general theory of relativity all by itself is inadequate. After all, how does the space-time metric know how to change in the presence of matter? There has to be some transcendent intelligent entity responsible for altering space-time whenever the distribution of energy in the universe changes, so we need to supplement the usual equations of GR with this additional theoretical posit in order to solve this problem. The correct response to this is that the supposed “problem” itself is a mistake stemming from unclear thinking, and that there is no need to posit this additional entity. And since the only motivation for positing this entity’s existence was the pseudo-problem we have just rejected, it would be a mistake to believe that the entity exists. Wallace’s (and I think Eliezer’s) position is that the quantum interpretation debates are just sophisticated versions of this.
* This is not to say that an anti-realist or instrumentalist attitude to scientific theories is a mistake, provided this attitude is a general philosophical position and not motivated by the supposed peculiarities of quantum mechanics. However, many people (e.g. Fuchs and Peres) who advocate instrumentalism about QM aren’t motivated by the attractions of instrumentalism per se but rather by a belief that there is something about quantum mechanics specifically that makes realism untenable. This is a mistake, according to Everettians.
I take Eliezer’s position on MWI to be pretty well expressed by this quote from David Wallace:
The central case for Everettianism is that it is just plain old quantum mechanics, approached with the default realist perspective that most of us have no problem adopting for practically every other physical theory.* Every other “interpretation” out there adds on extra posits—either ontological posits or epistemological posits that one doesn’t usually hear when talking about other theories—in order to solve a problem that doesn’t actually exist, the so-called “measurement problem”. So it’s not just that MWI is simpler than the other theories; it’s that the sole motivation for the added complexity in other theories—the supposed inadequacy of bare quantum theory to account for our observations—turns out to be bunk.
Suppose someone argued that the general theory of relativity all by itself is inadequate. After all, how does the space-time metric know how to change in the presence of matter? There has to be some transcendent intelligent entity responsible for altering space-time whenever the distribution of energy in the universe changes, so we need to supplement the usual equations of GR with this additional theoretical posit in order to solve this problem. The correct response to this is that the supposed “problem” itself is a mistake stemming from unclear thinking, and that there is no need to posit this additional entity. And since the only motivation for positing this entity’s existence was the pseudo-problem we have just rejected, it would be a mistake to believe that the entity exists. Wallace’s (and I think Eliezer’s) position is that the quantum interpretation debates are just sophisticated versions of this.
* This is not to say that an anti-realist or instrumentalist attitude to scientific theories is a mistake, provided this attitude is a general philosophical position and not motivated by the supposed peculiarities of quantum mechanics. However, many people (e.g. Fuchs and Peres) who advocate instrumentalism about QM aren’t motivated by the attractions of instrumentalism per se but rather by a belief that there is something about quantum mechanics specifically that makes realism untenable. This is a mistake, according to Everettians.