Ideas of Sextus Empiricus, by Theme

[Greek, 140 - 200, Probably a doctor.]

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1. Philosophy / F. Analytic Philosophy / 2. Analysis by Division
You cannot divide anything into many parts, because after the first division you are no longer dividing the original
     Full Idea: You cannot divide anything (such as the decad) into many parts, because as soon as you separate the first part, you are no longer dividing the original.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.215)
2. Reason / E. Argument / 6. Conclusive Proof
Proof moves from agreed premises to a non-evident inference
     Full Idea: Dogmatists define proof as "an argument which, by means of agreed premises, reveals by way of deduction a nonevident inference".
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.135)
3. Truth / A. Truth Problems / 5. Truth Bearers
It is only when we say a proposition that we speak truly or falsely
     Full Idea: It is only when we say a proposition that we speak truly or falsely.
     From: Sextus Empiricus (Against the Professors (six books) [c.180], 8.74)
     A reaction: This makes assertions truth-bearers, rather than propositions. But a proposition can be true or false if it is stamped with a date and/or place. "Shakespeare was born in Stratford on 23rd April 1664". No one needs to assert that.
5. Theory of Logic / B. Logical Consequence / 8. Material Implication
A valid hypothetical syllogism is 'that which does not begin with a truth and end with a falsehood'
     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.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.110)
     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'.
5. Theory of Logic / E. Structures of Logic / 1. Logical Form
'Man is a rational mortal animal' is equivalent to 'if something is a man, that thing is a rational mortal animal'
     Full Idea: Definitions are identical to universal propositions in meaning, and only differ in syntax, for whoever says 'Man is a rational mortal animal' says the same thing in meaning as whoever says 'If something is a man, that thing is a rational mortal animal'.
     From: Sextus Empiricus (Against the Professors (six books) [c.180], 11.8)
     A reaction: How strikingly like Bertrand Russell's interest and solutions. Sextus shows a straightforward interest in logical form, of a kind we associate with the twentieth century. Did Sextus Empiricus invent quantification?
5. Theory of Logic / L. Paradox / 7. Paradoxes of Time
Since Socrates either died when he was alive (a contradiction) or died when he was dead (meaningless), he didn't die
     Full Idea: If Socrates died, he died either when he lived or when he died; so he was either dead when he was alive, or he was twice dead when he was dead. So he didn't die.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.111)
     A reaction: One of my favourites. Of all the mysteries facing us, the one that boggles me most is how anything can happen in the 'present' moment, if the present is just the overlap point between past and future.
11. Knowledge Aims / B. Certain Knowledge / 2. Common Sense Certainty
If an argument has an absurd conclusion, we should not assent to the absurdity, but avoid the absurd argument
     Full Idea: If an argument leads to confessedly absurd conclusions, we should not assent to the absurdity just because of the argument, but avoid the argument because of the absurdity.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.252)
     A reaction: cf. G.E.Moore. Denying that you have a hand seems to be an absurdity, but I'm not sure if I can give a criterion for absurdity in such a case.
11. Knowledge Aims / C. Knowing Reality / 1. Perceptual Realism / c. Representative realism
Whether honey is essentially sweet may be doubted, as it is a matter of judgement rather than appearance
     Full Idea: Honey appears to sceptics to be sweet, but whether it is also sweet in its essence is for us a matter of doubt, since this is not an appearance but a judgement.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.20)
12. Knowledge Sources / B. Perception / 5. Interpretation
How can the intellect know if sensation is reliable if it doesn't directly see external objects?
     Full Idea: Just as you can't know if a portrait of Socrates is good without seeing the man, so when the intellect gazes on sensations but not the external objects it cannot know whether they are similar.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.75)
12. Knowledge Sources / D. Empiricism / 3. Pragmatism
We distinguish ambiguities by seeing what is useful
     Full Idea: It is the experience of what is useful in each affair that brings about the distinguishing of ambiguities.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.258)
13. Knowledge Criteria / B. Internal Justification / 4. Foundationalism / b. Basic beliefs
Some things are their own criterion, such as straightness, a set of scales, or light
     Full Idea: Dogmatists say something can be its own criterion. The straight is the standard of itself, and a set of scales establishes the equality of other things and of itself, and light seems to reveal not just other things but also itself.
     From: Sextus Empiricus (Against the Mathematicians [c.180], 442)
     A reaction: Each of these may be a bit dubious, but deserves careful discussion.
13. Knowledge Criteria / D. Scepticism / 1. Scepticism
The basis of scepticism is the claim that every proposition has an equal opposing proposition
     Full Idea: The main basic principle of the sceptic system is that of opposing to every proposition an equal proposition.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.12)
13. Knowledge Criteria / D. Scepticism / 3. Illusion Scepticism
The same tower appears round from a distance, but square close at hand
     Full Idea: The same tower appears round from a distance, but square close at hand.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.32)
The same oar seems bent in water and straight when out of it
     Full Idea: The same oar seems bent when in the water but straight when out of the water.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.119)
The necks of doves appear different in colour depending on the angle of viewing
     Full Idea: The necks of doves appear different in hue according to the differences in the angle of inclination.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.120)
If we press the side of an eyeball, objects appear a different shape
     Full Idea: When we press the eyeball at one side the forms, figures and sizes of the objects appear oblong and narrow.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.47)
13. Knowledge Criteria / D. Scepticism / 6. Scepticism Critique
How can sceptics show there is no criterion? Weak without, contradiction with
     Full Idea: The dogmatists ask how the sceptic can show there is no criterion. If without a criterion, he is untrustworthy; with a criterion he is turned upside down. He says there is no criterion, but accepts a criterion to establish this.
     From: Sextus Empiricus (Against the Mathematicians [c.180], 440)
     A reaction: This is also the classic difficulty for foundationalist views of knowledge. Is the foundation justified, or not?
13. Knowledge Criteria / E. Relativism / 1. Relativism
How can we judge between our impressions and those of other animals, when we ourselves are involved?
     Full Idea: We cannot judge between our own impressions and those of other animals, because we ourselves are involved in the dispute.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.59)
13. Knowledge Criteria / E. Relativism / 3. Subjectivism
Sickness is perfectly natural to the sick, so their natural perceptions should carry some weight
     Full Idea: Health is natural for the healthy but unnatural for the sick, and sickness is unnatural for the healthy but natural for the sick, so we must give credence to the natural perceptions of the sick.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.103)
If we enjoy different things, presumably we receive different impressions
     Full Idea: The enjoyment of different things is an indication that we get varying impressions from the underlying objects.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.80)
If we had no hearing or sight, we would assume no sound or sight exists, so there may be unsensed qualities
     Full Idea: A man with touch, taste and smell, but no hearing or sight, will assume nothing audible or visible exists, so maybe an apple has qualities which we have no senses to perceive.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.96)
Water that seems lukewarm can seem very hot on inflamed skin
     Full Idea: The same water which seems very hot when poured on inflamed spots seems lukewarm to us.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.101)
Some actions seem shameful when sober but not when drunk
     Full Idea: Actions which seem shameful to us when sober do not seem shameful when drunk.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.109)
13. Knowledge Criteria / E. Relativism / 4. Cultural relativism
With us it is shameful for men to wear earrings, but among Syrians it is considered noble
     Full Idea: It is a shameful thing with us for men to wear earrings, but among some of the barbarians, such as the Syrians, it is a token of nobility.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.203)
Even if all known nations agree on a practice, there may be unknown nations which disagree
     Full Idea: Even among practices on which all known cultures are agreed, disagreement about them may possibly exist amongst some of the nations which are unknown to us.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.234)
14. Science / A. Basis of Science / 1. Observation
How can you investigate without some preconception of your object?
     Full Idea: A preconception and conception must precede every object of investigation, for how can anyone even investigate without some conception of the object of investigation?
     From: Sextus Empiricus (Against the Professors (six books) [c.180], 8.331a)
     A reaction: The Duhem-Quine thesis about the 'theory-ladenness of observation' is just a revival of some routine ancient scepticism. As well as a conceptual scheme to accommodate the observation, there must also be some motivation for the investigation.
14. Science / C. Induction / 3. Limits of Induction
If you don't view every particular, you may miss the one which disproves your universal induction
     Full Idea: Induction cannot establish the universal by means of the particular, since limited particulars may omit crucial examples which disprove the universal, and infinite particulars are impossible to know.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.204)
18. Thought / A. Modes of Thought / 6. Judgement / a. Nature of Judgement
If we utter three steps of a logical argument, they never exist together
     Full Idea: If we say "If day exists, lights exists", and then "day exists", and then "light exists", then parts of the judgement never exist together, and so the whole judgement will have no real existence.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], II.109)
23. Ethics / B. Contract Ethics / 9. Contractualism
Right actions, once done, are those with a reasonable justification
     Full Idea: Right action is whatever, once it has been done, has a reasonable justification.
     From: Sextus Empiricus (Against the Professors (six books) [c.180], 7.158)
     A reaction: Why does he add 'once it has been done'? Wouldn't a proposed action be right if it had a reasonable justification? This grows out of the classical and Stoic emphasis on reason in ethics, and leads towards Scanlon's Contractualism.
26. Natural Theory / A. Speculations on Nature / 4. Mathematical Nature
The tektraktys (1+2+3+4=10) is the 'fount of ever-flowing nature'
     Full Idea: The tektraktys (1+2+3+4=10) is the 'fount of ever-flowing nature', because nature is a harmony of three concords (4th,5th and octave), and these ratios (4:3, 3:2, and 2:1) are found in the tektraktys.
     From: Sextus Empiricus (Against the Professors (six books) [c.180], 7.95)
26. Natural Theory / C. Causation / 4. Naturalised causation
Some say that causes are physical, some say not
     Full Idea: Some affirm cause to be corporeal, some incorporeal.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.14)
26. Natural Theory / C. Causation / 7. Eliminating causation
Knowing an effect results from a cause means knowing that the cause belongs with the effect, which is circular
     Full Idea: To know an effect belongs to a cause, we must also know that that cause belongs to that effect, and this is circular.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.21)
If there were no causes then everything would have been randomly produced by everything
     Full Idea: If causes were non-existent everything would have been produced by everything, and at random.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.18)
Cause can't exist before effect, or exist at the same time, so it doesn't exist
     Full Idea: If cause neither subsists before its effect, nor subsists along with it, nor does the effect precede the cause, it would seem that it has no substantial existence at all.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.27)
26. Natural Theory / C. Causation / 8. Particular Causation / c. Conditions of causation
Causes are either equal to the effect, or they link equally with other causes, or they contribute slightly
     Full Idea: The majority say causes are immediate (when they are directly proportional to effects), or associate (making an equal contribution to effects), or cooperant (making a slight contribution).
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.15)
27. Natural Reality / A. Classical Physics / 1. Mechanics / a. Explaining movement
Does the original self-mover push itself from behind, or pull itself from in front?
     Full Idea: Self-movement must move in some particular direction, but if it pushes it will be behind itself, and if it pulls it will be in front of itself.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.68)
     A reaction: This is the same as Aquinas's First Way of proving God's existence.
If time and place are infinitely divided, it becomes impossible for movement ever to begin
     Full Idea: If bodies, and the places and times when they are said to move, are divided into infinity, motion will not occur, it being impossible to find anything which will initiate the first movement.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.76)
If all atoms, times and places are the same, everything should move with equal velocity
     Full Idea: If objects are reducible to atoms, and each thing passes in an atomic time with its own first atom into an atomic point of space, then all moving things are of equal velocity.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.77)
27. Natural Reality / C. Space-Time / 2. Time / a. Time
How can time be divisible if we can't compare one length of time with another?
     Full Idea: Time is clearly divisible (into past, present and future), but it can't be, because a divisible thing is measured by some part of itself (divisions of length), but the two parts must coincide to make the measurement (e.g. present must coincide with past).
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.143)
27. Natural Reality / C. Space-Time / 2. Time / e. Existence of time
Time must be unlimited, but past and present can't be non-existent, and can't be now, so time does not exist
     Full Idea: There can't be a time when there was no time, so time is not limited; but unlimited time means past and present are non-existent (so time is limited to the present), or they exist (which means they are present). Time does not exist.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.142)
27. Natural Reality / C. Space-Time / 2. Time / i. Time and change
If motion and rest are abolished, so is time
     Full Idea: Since time does not seem to subsist without motion or even rest, if motion is abolished, and likewise rest, time is abolished.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.141)
28. God / A. Divine Nature / 2. Divine Nature
How can we agree on the concept of God, unless we agree on his substance or form or place?
     Full Idea: How shall we be able to reach a conception of God when we have no agreement about his substance or his form or his place of abode?
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.3)
28. God / B. Proving God / 2. Proofs of Reason / b. Ontological Proof critique
The existence of God can't be self-evident or everyone would have agreed on it, so it needs demonstration
     Full Idea: The existence of God is not pre-evident, for if it was the dogmatists would have agreed about it, whereas their disagreements show it is non-evident, and in need of demonstration.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.6)
29. Religion / D. Religious Issues / 3. Problem of Evil / d. Natural Evil
If God foresaw evil he would presumably prevent it, and if he only foresees some things, why those things?
     Full Idea: If God had forethought for all, there would be no evil in the world, yet they say the world is full of evil. And if he forethinks some things, why those and not others?
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.9)