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Single Idea 8078

[filed under theme 5. Theory of Logic / B. Logical Consequence / 5. Modus Ponens ]

Full Idea

Modus ponens is just one of the five different inference rules identified by the Stoics.

Clarification

'Modus ponens' says if p implies q, and p is true, then q must be true

Gist of Idea

Modus ponens is one of five inference rules identified by the Stoics

Source

report of Chrysippus (fragments/reports [c.240 BCE]) by Keith Devlin - Goodbye Descartes Ch.2

Book Ref

Devlin,Keith: 'Goodbye Descartes: the end of logic' [Wiley 1997], p.36

A Reaction

Modus ponens strikes me as being more like a definition of implication than a 'rule'. Implication is what gets you from one truth to another. All the implications of a truth must also be true.

The 60 ideas from Chrysippus

20853 Wise men should try to participate in politics, since they are a good influence [Chrysippus, by Diog. Laertius]
9199 Wisdom for one instant is as good as wisdom for eternity [Chrysippus]
20772 Three branches of philosophy: first logic, second ethics, third physics (which ends with theology) [Chrysippus]
5969 Chrysippus said the uncaused is non-existent [Chrysippus, by Plutarch]
21388 The causes of future true events must exist now, so they will happen because of destiny [Chrysippus, by Cicero]
20780 Graspable presentations are criteria of facts, and are molded according to their objects [Chrysippus, by Diog. Laertius]
20793 How could you ever know that the presentation is similar to the object? [Sext.Empiricus on Chrysippus]
8077 Stoic propositional logic is like chemistry - how atoms make molecules, not the innards of atoms [Chrysippus, by Devlin]
20791 Chrysippus has five obvious 'indemonstrables' of reasoning [Chrysippus, by Diog. Laertius]
8078 Modus ponens is one of five inference rules identified by the Stoics [Chrysippus, by Devlin]
6023 Every proposition is either true or false [Chrysippus, by Cicero]
5992 Chrysippus says action is the criterion for existence, which must be physical [Chrysippus, by Tieleman]
21673 There are simple and complex facts; the latter depend on further facts [Chrysippus, by Cicero]
16652 Stoics categories are Substrate, Quality, Disposition, and Relation [Chrysippus, by Pasnau]
16058 Dion and Theon coexist, but Theon lacks a foot. If Dion loses a foot, he ousts Theon? [Chrysippus, by Philo of Alexandria]
20808 Everything is fated, either by continuous causes or by a supreme rational principle [Chrysippus, by Diog. Laertius]
20837 Fate is an eternal and fixed chain of causal events [Chrysippus]
16059 Change of matter doesn't destroy identity - in Dion and Theon change is a condition of identity [Chrysippus, by Long/Sedley]
3044 Stoics say that beauty and goodness are equivalent and linked [Chrysippus, by Diog. Laertius]
1875 Dogs show reason in decisions made by elimination [Chrysippus, by Sext.Empiricus]
20834 Chrysippus allows evil to say it is fated, or even that it is rational and natural [Plutarch on Chrysippus]
20833 A swerve in the atoms would be unnatural, like scales settling differently for no reason [Chrysippus, by Plutarch]
20835 Chrysippus is wrong to believe in non-occurring future possibilities if he is a fatalist [Plutarch on Chrysippus]
20836 The Lazy Argument responds to fate with 'why bother?', but the bothering is also fated [Chrysippus, by Cicero]
21679 When we say events are fated by antecedent causes, do we mean principal or auxiliary causes? [Chrysippus]
1782 Stoics teach that God is a unity, variously known as Mind, or Fate, or Jupiter [Chrysippus, by Diog. Laertius]
20787 A proposition is what can be asserted or denied on its own [Chrysippus]
20850 Passions are judgements; greed thinks money is honorable, and likewise drinking and lust [Chrysippus, by Diog. Laertius]
20869 The highest degree of morality performs all that is appropriate, omitting nothing [Chrysippus]
20838 Fate initiates general causes, but individual wills and characters dictate what we do [Chrysippus]
20813 Human purpose is to contemplate and imitate the cosmos [Chrysippus]
3045 Stoics say justice is a part of nature, not just an invented principle [Chrysippus, by Diog. Laertius]
20774 Only nature is available to guide action and virtue [Chrysippus]
20864 Live in agreement, according to experience of natural events [Chrysippus]
20855 Chrysippus says virtue can be lost (though Cleanthes says it is too secure for that) [Chrysippus, by Diog. Laertius]
5970 Chrysippus says nothing is blameworthy, as everything conforms with the best nature [Chrysippus, by Plutarch]
20842 Rational animals begin uncorrupted, but externals and companions are bad influences [Chrysippus, by Diog. Laertius]
3042 Stoics teach that law is identical with right reason, which is the will of Zeus [Chrysippus, by Diog. Laertius]
20856 Justice, the law, and right reason are natural and not conventional [Chrysippus, by Diog. Laertius]
1779 We don't have obligations to animals as they aren't like us [Chrysippus, by Diog. Laertius]
20857 Justice is irrelevant to animals, because they are too unlike us [Chrysippus, by Diog. Laertius]
20812 Covers are for shields, and sheaths for swords; likewise, all in the cosmos is for some other thing [Chrysippus]
21403 The later Stoics identified the logos with an air-fire compound, called 'pneuma' [Chrysippus, by Long]
20828 Fire is a separate element, not formed with others (as was previously believed) [Chrysippus, by Stobaeus]
1777 Pleasure is not the good, because there are disgraceful pleasures [Chrysippus, by Diog. Laertius]
20845 There are shameful pleasures, and nothing shameful is good, so pleasure is not a good [Chrysippus, by Diog. Laertius]
5967 People need nothing except corn and water [Chrysippus, by Plutarch]
20819 The past and the future subsist, but only the present exists [Chrysippus, by Plutarch]
20818 The present does not exist, so our immediate experience is actually part past and part future [Chrysippus, by Plutarch]
20821 Time is continous and infinitely divisible, so there cannot be a wholly present time [Chrysippus, by Stobaeus]
3048 Stoics say that God the creator is the perfection of all animals [Chrysippus, by Diog. Laertius]
20773 The origin of justice can only be in Zeus, and in nature [Chrysippus]
20830 Death can't separate soul from body, because incorporeal soul can't unite with body [Chrysippus]
21404 There is a rationale in terrible disasters; they are useful to the whole, and make good possible [Chrysippus]
5966 All virtue is good, but not always praised (as in not lusting after someone ugly) [Chrysippus]
5973 Justice can be preserved if pleasure is a good, but not if it is the goal [Chrysippus, by Plutarch]
5965 The source of all justice is Zeus and the universal nature [Chrysippus]
5975 Stoics say earth, air, fire and water are the primary elements [Chrysippus, by Plutarch]
5971 Destiny is only a predisposing cause, not a sufficient cause [Chrysippus, by Plutarch]
5972 Living happily is nothing but living virtuously [Chrysippus, by Plutarch]