Stoic Logic - basic intro

 

There are actually two systems of logic in the classical world.

Stoic and Aristotelian.

 

This page covers some basic ideas of Stoic logic. 

Stoic L is also sometimes called Propositional Logic.

 

Stoic Logic was first developed by Chrysippus, in the 3rd-century BC.

It's teachings were "lost" for many centuries and only rediscovered in the 20th century .

The first person to reappraise their ideas was the Polish logician Jan Łukasiewicz.

 

There appear to be close similarities between the methods of Stoic reasoning and the behaviour of digital computers. ... The code of the nineteeth-century logician and mathematician George Boole bear much in common with Chrysippus. Propositional logic is thus closely related to modern mathematical & Boolean logic.

 

Stoic logic is different from Aristotle's term logic because it was based on the analysis of propositions rather than terms.

 

Aristotelian logic uses terms like all Xs are Ys, some Xs are Ys, and no Xs are Ys

A example is: All men are mortal. Dion is a man.

A conclusion is reached by rules known as Syllogisms.

eg: Therefore, Dion is a mortal.. 

 

Propositional logic uses Propositions. (statements that are either true or false)

It also uses operators ( logical connectives) like the Conditional, Paraconditional, Conjunction, and Disjunction, etc

An example: 

If X then Y; 

Both X and Y; 

Either X or Y. 

These propositions and operators can be combined to create more advanced statements too, like: If A and B, and C or D, then it is not the case that E.

 

So to summarise:

Stoic Logic a system of deduction which uses 2 parts:

1. propositions (statements that are either true or false)

2. operators or logical connectives (which act upon the propositions). 

 

Stoic logic starts with simple propositions. A favorite examples from the ancient texts:

• Dion is walking.

 We can turn this into a complex proposition by using an "operator".

These are really similar to boolean operators

Boolean Operators are simple words (AND, OR, NOT or AND NOT) used as conjunctions to combine or exclude keywords in a search

 

Stoic  propositions "operators" use terms like:

 

    Conditional (if) :                                        If it is day, it is light.
    Paraconditional/Pseudoconditional (since): Since it is day, it is light.
    Conjunction (and) :                                    Both it is day and it is night.
    Disjunction (either ... or) :                          Either it is day or it is night.
    Causal (because) :                                     Because it is day, it is light.

    Comparative (more/less likely .... than  :     more likely it is day than night     

    The more: It is more day than it is night.
    The less: It is less night than it is day.
 

 

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