====Version 1. “On the Natural Classification of Arguments” (1867)====
====Version 1. “On the Natural Classification of Arguments” (1867)====
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{| align="center" width="90%"
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<p>The formula of analogy is as follows:</p>
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<p> ''S′, S′′, S′′′'' are taken at random from such a class that their characters at random are such as ''P′, P′′, P′′′.''</p>
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====Version 2. “A Theory of Probable Inference” (1883)====
====Version 2. “A Theory of Probable Inference” (1883)====