Suppose that a digital computer is having a conscious experience. We could then make an exact copy of this conscious experience and run it on a second computer. Does this act have any moral significance? If the experience is a happy one, have we increased the amount of happiness in the world? If the experience is a painful one, have we increased the amount of pain?

It is plausible that we should answer "no" to each of the above questions. The argument for this view claims that the question "How many physical copies of a conscious experience are there?" is not well defined, and therefore cannot matter. I will refer to this as the Ignore-Copies view.

The purpose of this post is to explore what I think is a tension between the Ignore-Copies view, and the Many-Worlds Interpretation of Quantum Mechanics (MWI).

Intuition behind the tension

I think the fastest way to convey the intuition behind why there might be a tension here is to consider something which is not the Many Worlds Interpretation of Quantum Mechanics:

Not the Many-Worlds Interpretation: When quantum mechanics predicts that outcome A is twice as likely as outcome B, this is because twice as many (otherwise identical) copies of you experience outcome A as experience outcome B.

Importantly, this is not how MWI actually works, but suppose for the moment that it was. Hopefully the tension between this statement and the Ignore-Copies view is clear. On the one hand, we have an argument that the question "How many physical copies of a conscious experience are there?" is not well defined. On the other hand, we have an argument that questions of this kind are ultimately responsible for some of the most well tested empirical predictions in all of science.

In the rest of this post, I will review what MWI actually involves, and I will argue that there really is a tension between MWI and the Ignore-Copies view. It is not simply an artefact of my butchered re-statement of MWI above. I argue that some of the most appealing ways to derive the Born rule for quantum mechanical probabilities in MWI are seriously undermined by the Ignore-Copies view.

This is something that has bothered me for a while, although I've not seen this tension explicitly referred to anywhere else. I've only recently decided to spend a little bit of time digging into some of the literature on these questions to see if I could resolve my confusion. I have come away feeling that the tension is real, and thought some people might be interested enough to justify sharing this write up.

I imagine a lot of people will not find this particularly interesting, but if like me you put non-negligible credence in each of the following propositions:

• It is possible for conscious experiences to be perfectly copied (this follows, for example, if it is possible for a digital computer to be conscious).
• Exact copies of conscious experiences carry no extra moral weight.
• MWI is correct.

then this tension seems worth understanding. Is it resolvable?

(continued in linked post)