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Single Idea 12196
[filed under theme 5. Theory of Logic / B. Logical Consequence / 8. Material Implication
]
Full Idea
Philo (of Megara) says that a valid hypothetical syllogism is 'that which does not begin with a truth and end with a falsehood,' as for instance the syllogism 'If it is day, I converse,' when in fact it is day and I am conversing.
Gist of Idea
A valid hypothetical syllogism is 'that which does not begin with a truth and end with a falsehood'
Source
Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.110)
Book Ref
Sextus Empiricus: 'Outlines of Pyrrhonism', ed/tr. Bury,R.G. [Prometheus 1990], p.132
A Reaction
Russell endorses this, and Rumfitt quotes it as the classic case of denying that there is any modal aspect (such as 'logical necessity') involved in logical consequence. He labels it 'material or Philonian consequence'.
The
73 ideas
from Sextus Empiricus
22752
|
Reasoning is impossible without a preconception
[Sext.Empiricus]
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22754
|
Saying the good is useful or choiceworth or happiness-creating is not the good, but a feature of it
[Sext.Empiricus]
|
22755
|
Like a warming fire, what is good by nature should be good for everyone
[Sext.Empiricus]
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22756
|
If a desire is itself desirable, then we shouldn't desire it, as achieving it destroys it
[Sext.Empiricus]
|
22759
|
Fools, infants and madmen may speak truly, but do not know
[Sext.Empiricus]
|
22760
|
Madmen are reliable reporters of what appears to them
[Sext.Empiricus]
|
22762
|
Some properties are inseparable from a thing, such as the length, breadth and depth of a body
[Sext.Empiricus]
|
22763
|
We can only dream of a winged man if we have experienced men and some winged thing
[Sext.Empiricus]
|
22764
|
Ordinary speech is not exact about what is true; we say we are digging a well before the well exists
[Sext.Empiricus]
|
20794
|
How can sceptics show there is no criterion? Weak without, contradiction with
[Sext.Empiricus]
|
20795
|
Some things are their own criterion, such as straightness, a set of scales, or light
[Sext.Empiricus]
|
22728
|
Gods were invented as watchers of people's secret actions
[Sext.Empiricus]
|
22730
|
All men agree that God is blessed, imperishable, happy and good
[Sext.Empiricus]
|
22731
|
It is mad to think that what is useful to us, like lakes and rivers, are gods
[Sext.Empiricus]
|
22732
|
The perfections of God were extrapolations from mankind
[Sext.Empiricus]
|
22734
|
God is defended by agreement, order, absurdity of denying God, and refutations
[Sext.Empiricus]
|
22735
|
The original substance lacked motion or shape, and was given these by a cause
[Sext.Empiricus]
|
22736
|
God's sensations imply change, and hence perishing, which is absurd, so there is no such God
[Sext.Empiricus]
|
22738
|
The Divine must lack the virtues of continence and fortitude, because they are not needed
[Sext.Empiricus]
|
22737
|
An incorporeal God could do nothing, and a bodily god would perish, so there is no God
[Sext.Empiricus]
|
22739
|
God must suffer to understand suffering
[Sext.Empiricus]
|
22740
|
God without virtue is absurd, but God's virtues will be better than God
[Sext.Empiricus]
|
22741
|
The incorporeal is not in the nature of body, and so could not emerge from it
[Sext.Empiricus]
|
22742
|
Socrates either dies when he exists (before his death) or when he doesn't (after his death)
[Sext.Empiricus]
|
22744
|
Parts are not parts if their whole is nothing more than the parts
[Sext.Empiricus]
|
22746
|
If we try to conceive of a line with no breadth, it ceases to exist, and so has no length
[Sext.Empiricus]
|
22747
|
A man walking backwards on a forwards-moving ship is moving in a fixed place
[Sext.Empiricus]
|
22748
|
Some say motion is perceived by sense, but others say it is by intellect
[Sext.Empiricus]
|
22749
|
Time doesn't end with the Universe, because tensed statements about destruction remain true
[Sext.Empiricus]
|
22750
|
Time is divisible, into past, present and future
[Sext.Empiricus]
|
22751
|
If the present is just the limit of the past or the future, it can't exist because they don't exist
[Sext.Empiricus]
|
6020
|
'Man is a rational mortal animal' is equivalent to 'if something is a man, that thing is a rational mortal animal'
[Sext.Empiricus]
|
6032
|
Right actions, once done, are those with a reasonable justification
[Sext.Empiricus]
|
1517
|
The tektraktys (1+2+3+4=10) is the 'fount of ever-flowing nature'
[Sext.Empiricus]
|
6026
|
How can you investigate without some preconception of your object?
[Sext.Empiricus]
|
6021
|
It is only when we say a proposition that we speak truly or falsely
[Sext.Empiricus]
|
1878
|
Water that seems lukewarm can seem very hot on inflamed skin
[Sext.Empiricus]
|
1879
|
Sickness is perfectly natural to the sick, so their natural perceptions should carry some weight
[Sext.Empiricus]
|
1880
|
Some actions seem shameful when sober but not when drunk
[Sext.Empiricus]
|
1881
|
The same oar seems bent in water and straight when out of it
[Sext.Empiricus]
|
1870
|
The basis of scepticism is the claim that every proposition has an equal opposing proposition
[Sext.Empiricus]
|
1882
|
The necks of doves appear different in colour depending on the angle of viewing
[Sext.Empiricus]
|
1871
|
Whether honey is essentially sweet may be doubted, as it is a matter of judgement rather than appearance
[Sext.Empiricus]
|
1872
|
The same tower appears round from a distance, but square close at hand
[Sext.Empiricus]
|
1873
|
If we press the side of an eyeball, objects appear a different shape
[Sext.Empiricus]
|
1874
|
How can we judge between our impressions and those of other animals, when we ourselves are involved?
[Sext.Empiricus]
|
1876
|
If we enjoy different things, presumably we receive different impressions
[Sext.Empiricus]
|
1877
|
If we had no hearing or sight, we would assume no sound or sight exists, so there may be unsensed qualities
[Sext.Empiricus]
|
1884
|
If we utter three steps of a logical argument, they never exist together
[Sext.Empiricus]
|
12196
|
A valid hypothetical syllogism is 'that which does not begin with a truth and end with a falsehood'
[Sext.Empiricus]
|
1885
|
Proof moves from agreed premises to a non-evident inference
[Sext.Empiricus]
|
1886
|
If you don't view every particular, you may miss the one which disproves your universal induction
[Sext.Empiricus]
|
1887
|
You cannot divide anything into many parts, because after the first division you are no longer dividing the original
[Sext.Empiricus]
|
1889
|
If an argument has an absurd conclusion, we should not assent to the absurdity, but avoid the absurd argument
[Sext.Empiricus]
|
1890
|
We distinguish ambiguities by seeing what is useful
[Sext.Empiricus]
|
1883
|
How can the intellect know if sensation is reliable if it doesn't directly see external objects?
[Sext.Empiricus]
|
1902
|
Since Socrates either died when he was alive (a contradiction) or died when he was dead (meaningless), he didn't die
[Sext.Empiricus]
|
1894
|
Some say that causes are physical, some say not
[Sext.Empiricus]
|
1903
|
If motion and rest are abolished, so is time
[Sext.Empiricus]
|
1904
|
Time must be unlimited, but past and present can't be non-existent, and can't be now, so time does not exist
[Sext.Empiricus]
|
1905
|
How can time be divisible if we can't compare one length of time with another?
[Sext.Empiricus]
|
1895
|
Causes are either equal to the effect, or they link equally with other causes, or they contribute slightly
[Sext.Empiricus]
|
1896
|
If there were no causes then everything would have been randomly produced by everything
[Sext.Empiricus]
|
1910
|
With us it is shameful for men to wear earrings, but among Syrians it is considered noble
[Sext.Empiricus]
|
1897
|
Knowing an effect results from a cause means knowing that the cause belongs with the effect, which is circular
[Sext.Empiricus]
|
1911
|
Even if all known nations agree on a practice, there may be unknown nations which disagree
[Sext.Empiricus]
|
1898
|
Cause can't exist before effect, or exist at the same time, so it doesn't exist
[Sext.Empiricus]
|
1891
|
How can we agree on the concept of God, unless we agree on his substance or form or place?
[Sext.Empiricus]
|
1892
|
The existence of God can't be self-evident or everyone would have agreed on it, so it needs demonstration
[Sext.Empiricus]
|
1899
|
Does the original self-mover push itself from behind, or pull itself from in front?
[Sext.Empiricus]
|
1900
|
If time and place are infinitely divided, it becomes impossible for movement ever to begin
[Sext.Empiricus]
|
1901
|
If all atoms, times and places are the same, everything should move with equal velocity
[Sext.Empiricus]
|
1893
|
If God foresaw evil he would presumably prevent it, and if he only foresees some things, why those things?
[Sext.Empiricus]
|