A Boltzmann brain is a randomly-formed configuration of matter that is conscious. According to some theories that cosmologists take seriously, the universe is so spatiotemporally large that it contains a great many Boltzmann brains that are duplicates of you. In the light of this it seems to follow that you should have significant confidence that you are a Boltzmann brain. What's worse, your situation seems to be “cognitively unstable”: It seems unstable to end up confident that you are a Boltzmann brain because you should then think that your apparent cosmological evidence was randomly generated and hence that your confidence was unwarranted. But it also seems unstable to end up confident that you are not a Boltzmann brain because then you should follow your cosmological evidence to the conclusion that many Boltzmann brain duplicates of you exist, and hence that you are probably a Boltzmann brain. A case involving unreliable vision exhibits a similar threat of instability. A simple Bayesian model of that case, however, shows that the threat is an illusion. And a corresponding model suggests that the same goes for the threat of instability associated with Boltzmann brains.

中文翻译：

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玻尔兹曼脑和认知不稳定


玻尔兹曼脑是有意识的物质的随机形成配置。根据宇宙学家认真对待的一些理论，宇宙在时空上是如此之大，以至于它包含了许多玻尔兹曼大脑，这些大脑是你的复制品。有鉴于此，似乎你应该对自己是一个玻尔兹曼大脑有很大的信心。更糟糕的是，你的情况似乎是“认知不稳定”的：最终确信自己是玻尔兹曼大脑似乎很不稳定，因为你应该认为你明显的宇宙学证据是随机产生的，因此你的信心是没有根据的。但是，最终确信你不是玻尔兹曼大脑似乎也不稳定，因为那样你应该遵循你的宇宙学证据得出结论，即存在许多你的玻尔兹曼大脑副本，因此你可能是一个玻尔兹曼大脑。涉及不可靠视力的案例也表现出类似的不稳定威胁。然而，该案例的简单贝叶斯模型表明，威胁是一种幻觉。相应的模型表明，与玻尔兹曼大脑相关的不稳定威胁也是如此。