A century after the birth of quantum mechanics, many are still puzzled by the idea that Schrödinger’s cat is simultaneously alive and dead. The mystery drives some of our most prominent physicists to embrace the bizarre idea that reality constantly splits into a near infinity of parallel worlds, of which ours is just one. Philosopher of physics Nadia Blackshaw argues that this “many worlds” interpretation goes wrong not only in its extravagant multiplying of entities, but in its attempt to adopt a “view from nowhere,” describing reality from no particular perspective. She proposes instead a “many minds” interpretation, in which the cat is alive from one perspective and dead from another. It’s time physics took conscious perspectives seriously.

We like to tell the story of Schrödinger’s cat as if it is a puzzle about physics. There is a sealed box, a quantum event, a cat that is (according to the mathematics) both alive and dead until someone looks. But what is it like to be the cat?

Inside the box there is no equation, no observer, no paradox, just an experience. And it seems very unlikely that the cat is thinking or experiencing being in that multiple dead-and-alive superposition state. Experience, as far as we know, never feels like two incompatible things at once. We never remember a day when the cat was both alive and dead or when the coin both landed heads and tails. Quantum physics, meanwhile, describes the world as having these strange indefinite states, where coins or cats are two (or more!) things at once. Of course, this might also be saying that the cat is neither dead nor alive. But that still opens the question of what the cat is. So, the tension appears where the world, according to the theory, contains many possibilities at once, but each mind seems to encounter only one.

This gap between our physics and observations or experience of the world encapsulates the quantum measurement problem. And for nearly a century, physicists and philosophers have been trying to bridge it.

One popular solution is the Many Worlds Interpretation (MWI), first proposed by Hugh Everett III in 1957. If quantum mechanics says the cat is both alive and dead, the MWI takes this seriously: the cat really is both. The catch is that the universe splits or branches. In one branch, you open the box to find a living cat. In another branch, you find a dead one. Every quantum event creates new branches, and so we have an ever-expanding multiverse of parallel realities.

This is bold physics and philosophy, and it is also, to many, wildly extravagant. The universe doesn’t just split occasionally, because quantum events are ubiquitous in nature. The world is therefore constantly branching with every quantum interaction throughout the entire universe, generating uncountable parallel worlds. Yet, despite its radical nature, the MWI is taken to be a serious contender in the debate, and has many advocates. Setting aside specific concerns about parsimony or other questions surrounding probability in a theory where every outcome occurs, here I want to highlight a different drawback.

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There is one underlying physical reality, but within that we can explain the quantum description of the cat being both dead and alive, as pointing towards multiple, branching minds.

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