SylloGizmo SylloGizmo v1.2

Download SylloGizmo

SylloGizmo is a logic calculator for finding mood and figure of
a classical Aristotelian syllogism. SylloGizmo also verifies the
validity of the syllogism and shows the mnemonic, e.g. 'Barbara' or 'Ferio' etc.

NB: such a mnemonic exists for all valid syllogisms, and for most valid only with strengthening premise. The mnemonic is shown, of course, only for those syllogism that have one.

If the syllogism requires an additional strengthening (existential)
premise, such as "There exist Spartans", then SylloGizmo will report
that, too.

SylloGizmo is a handy gizmo for anyone learning about syllogisms. It
is especially useful for high-school or college students learning
about syllogism in a logic, debate, philosophy or math class.

A future version will include drawing the Square of Opposition and the Venn diagram illustrating the syllogism.

Known bugs: Japanese localization very incomplete.

See Wikipedia on Syllogisms or Friesian On Syllogisms for info on syllogisms and the terminology.


Parental rating: 
Everyone (age 6 and over)
Default language: 
Supported languages: 
Japanese, Spanish
Trial version: 
"In-App" billing: 
With advertisements: 
Terms And Conditions/Copyright: 

As in Apache License 2.0

Privacy policy: 

SylloGizmo uses no private information, so it collects none.



Requires Google Play and/or account: 
Requires third-party libraries: 
Requires 'rooted' device: 
Minimum Android version: 
Android 1.1
Minimum screen width: 
320 dpx
Requires features: 
Requires permissions: 
Write external storage, Read phone state, Read external storage

Discussions on SylloGizmo

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Syllogisms in Logic Classes: the "Existential Fallacy"

When I took logic back in college, we did not go into that much detail, so I would like SylloGizmo users (I see there have been 70 downloads already) to tell me how the issue is being covered in their classes. I refer to the issue sometimes called, "the existential fallacy", i.e., the fact that without a "strengthening premise", the syllogisms Darapti, Bramantip and a few others are not valid: unless elements of both classes actually exist, the conclusion does not follow from the premises.

Now my primary source on Syllogisms, Quine's excellent book "Methods of Logic" has a logically simple way of dealing with the issue, but I do not see the same language being used either on Wikipedia or anywhere else on the web. That is why I am asking you users: do your classes/texts use the same approach as the Wikipedia article? As the Friesian article? Or do they dismiss Darapti etc. as invalid with no further discussion? Do they even discuss the difference between propositions as descriptions of classes, and as descriptions of properties?

BTW: one of the curious differences between Quine and all these other sources is: his list of premises valid with a strengthening existential premise is bigger. Wikipedia lists only 4, but Quine lists several more, i.e. AAI-1, EAO-1, EAO-2, AEO-2, and AEO-4.

I am sure Quine is right, these too are valid; my guess is that others left them out because they are too trivial.

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Reviews of SylloGizmo

SylloGizmo is a terrific vehicle for waking up our brains. The user interface is straightforward, intuitive, and graphically pleasing. Novices should have no trouble using SylloGizmo. Using it for a short while has led me to a good understanding of syllogisms. With the educational need satisfied, I am finding endless entertainment changing nouns and running through the premises and conclusions.

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