The rational expectations revolution was not only based on the introduction of Muth’s idea of rational expectations to macroeconomics; the introduction of Muth’s hypothesis cannot explain the more drastic change of the mathematical toolbox and concepts, research strategies, vocabulary, and questions since the 1980s. The main claim is that the shift from “Keynesian economics†to “new classical economics†is based on a shift from a control engineering approach to an information engineering methodology. The paper even shows that the “revolution†was more radical. The change of engineering tools has changed macroeconomics more deeply, not only its methodology but also its epistemology and ontology. To show this shift in epistemology and ontology, the history of economics will be interwoven with the history of mathematics which cannot be detangled from the emergence of the digital computer and the influence of this emergence on the changed nature of mathematics: the adoption of a new concept of solution, no longer a number, a formula, or a function, but an algorithm. The result of this new concept of solution was a new approach to the analysis of processes. Information engineering studies the fundamental limits in communication and finds its origins in Shannon’s theory of communication, and incorporates the tools designed by Turing, Shannon, KAilmAin, and Bellman. The resulting ontology of this kind of engineering is a world populated by machines that communicate with each other by exchanging information. This information does not, however, contain only signals about the system states but also noise that needs to be filtered out. It is not a deterministic world, but one governed by stochastic processes. The decisions these machines take is conditioned on the (noisy) information they have about the current state of the world but at the same time will affect future states. Policy in this world therefore means tracing an optimal trajectory taking all these issues into account.

中文翻译：

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塑造理性预期革命的工程工具

理性预期革命不仅基于将穆特的理性预期思想引入宏观经济学；Muth 假设的引入无法解释自 1980 年代以来数学工具箱和概念、研究策略、词汇和问题的更剧烈的变化。主要主张是，从“凯恩斯经济学”到“新古典经济学”的转变是基于从控制工程方法到信息工程方法的转变。该论文甚至表明，“革命”更为激进。工程工具的变化更深刻地改变了宏观经济学，不仅是它的方法论，还有它的认识论和本体论。为了显示认识论和本体论的这种转变，经济学史将与数学史交织在一起，这无法从数字计算机的出现以及这种出现对数学性质改变的影响中解脱出来：采用新的解法概念，不再是数字，一个公式，或者一个函数，而是一个算法。这种新的解决方案概念的结果是一种新的过程分析方法。信息工程研究通信的基本限制，并在香农的通信理论中找到它的起源，并结合了图灵、香农、KAilmAin 和 Bellman 设计的工具。这种工程的最终本体是一个由通过交换信息相互通信的机器组成的世界。然而，这些信息并不 仅包含有关系统状态的信号，但也包含需要滤除的噪声。它不是一个确定性的世界，而是一个受随机过程支配的世界。这些机器做出的决定取决于它们对世界当前状态的（嘈杂）信息，但同时也会影响未来的状态。因此，这个世界的政策意味着在考虑所有这些问题的情况下追踪最佳轨迹。