Logica Demonstrativa

work by Saccheri

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June 30, 2026

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The Logica Demonstrativa (1697), or "Demonstrative Logic," was a work by the Italian Jesuit Gerolamo Saccheri. It presented logic in a manner similar to Euclid's geometric approach, using demonstrations, postulates, and definitions.12

Saccheri is more widely recognized for his later work, Euclides ab Omni Naevo Vindicatus (1733), where he explored the implications of altering Euclid's fifth postulate. This exploration led him to discover theorems that are now considered part of non-Euclidean geometry, even though his intention was to disprove such alternatives.13

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history of logic
The 17th century
…in the otherwise quite traditional Logica Demonstrativa (1697; “Demonstrative Logic”) of the Italian Jesuit Gerolamo Saccheri. Saccheri is better known for his suggestion of the possibility of a non-Euclidean geometry in Euclides ab Omni Naevo Vindicatus (1733; “Euclid Cleared of Every Flaw”). Another incisive traditional logic was that of the…
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…in the otherwise quite traditional Logica Demonstrativa (1697; “Demonstrative Logic”) of the Italian Jesuit Gerolamo Saccheri. Saccheri is better known for his suggestion of the possibility of a non-Euclidean geometry in Euclides ab Omni Naevo Vindicatus (1733; “Euclid Cleared of Every Flaw”). Another incisive traditional logic was that of the…
Read More