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Back to the ancients to find the future of science

Online Syllogism Solver

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This page features an automation of categorical syllogistic logic, a web based syllogistic machine for exploring fallacies, figures, terms, and modes of syllogisms. Syllogistic logic was first developed by Aristotle and later refined by the Scholastics during the Middle Ages. Use of this syllogistic machine is self-explanatory. An exciting version of Stoic logic coming soon!

Notes on Syllogistic Logic


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  • Danielle November 11, 2014, 3:00 am

    Wow, this online syllogism solver is amazing!!!! Thank you, it was so helpful for my philosophy class! The one thing I wish it would say is whether or not the syllogism is unconditionally or conditionally valid.

  • tester March 20, 2015, 5:47 pm

    Csharp application that gives results with drawings of syllogisms:

  • Nnaji November 24, 2015, 7:31 pm

    Online syllogism solver has been a great help in my philosophy class.

  • Lee February 15, 2017, 4:46 am

    I’m not sure this generator is reliable. For example, it says AAI-1 syllogisms are valid but they are not since they commit the existential fallacy. You cannot derive a particular conclusion (Some _ are _) from two universals (All _ are _ in both premises in this case). They can be conditionally valid from the Aristotelian standpoint, but then we would have to go back and check if the subject terms of the universals actually exist. This eliminates the possibility of constructing a formal system. From the Modern/Boolean standpoint, which is a completely formal system, syllogisms that commit the existential fallacy are always invalid. I know the title of this blog includes reference to the ancients but I believe there is general consensus that the modern standpoint is the better one and fixes problems in the Aristotelian system. At the very least, if the generator is using the Aristotelian standpoint, all of the forms that commit the existential fallacy should be classified as conditionally valid.

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