# The probability statements made by quantum mechanics are irreducible in the sense that they don't just reflect our limited knowledge of some hidden variables. In classical physics, probabilities were used to describe the outcome of rolling a die, even though the process was thought to be deterministic. Probabilities were used to substitute for complete knowledge. By contrast, the Copenhagen interpretation holds that in quantum mechanics, measurement outcomes are fundamentally indeterministic. |

# The probability statements made by quantum mechanics are irreducible in the sense that they don't just reflect our limited knowledge of some hidden variables. In classical physics, probabilities were used to describe the outcome of rolling a die, even though the process was thought to be deterministic. Probabilities were used to substitute for complete knowledge. By contrast, the Copenhagen interpretation holds that in quantum mechanics, measurement outcomes are fundamentally indeterministic. |

Schrödinger's cat was originally intended as an example to show how absurd the model was |

Schrödinger's cat was originally intended as an example to show how absurd the model was |

* [Physics FAQ section about Bell's inequality] |

* [Physics FAQ section about Bell's inequality] |