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
1. Philosophy / F. Analytic Philosophy / 5. Linguistic Analysis
Ordinary speech is not exact about what is true; we say we are digging a well before the well exists
2. Reason / A. Nature of Reason / 9. Limits of Reason
Reasoning is impossible without a preconception
2. Reason / E. Argument / 6. Conclusive Proof
Proof moves from agreed premises to a non-evident inference
3. Truth / A. Truth Problems / 5. Truth Bearers
It is only when we say a proposition that we speak truly or falsely
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'
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'
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
9. Objects / C. Structure of Objects / 8. Parts of Objects / c. Wholes from parts
Parts are not parts if their whole is nothing more than the parts
9. Objects / D. Essence of Objects / 9. Essence and Properties
Some properties are inseparable from a thing, such as the length, breadth and depth of a body
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
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
12. Knowledge Sources / B. Perception / 5. Interpretation
How can the intellect know if sensation is reliable if it doesn't directly see external objects?
12. Knowledge Sources / C. Rationalism / 1. Rationalism
Some say motion is perceived by sense, but others say it is by intellect
12. Knowledge Sources / D. Empiricism / 3. Pragmatism
We distinguish ambiguities by seeing what is useful
13. Knowledge Criteria / A. Justification Problems / 1. Justification / b. Need for justification
Fools, infants and madmen may speak truly, but do not know
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
13. Knowledge Criteria / C. External Justification / 3. Reliabilism / a. Reliable knowledge
Madmen are reliable reporters of what appears to them
13. Knowledge Criteria / D. Scepticism / 1. Scepticism
The basis of scepticism is the claim that every proposition has an equal opposing proposition
13. Knowledge Criteria / D. Scepticism / 3. Illusion Scepticism
The same oar seems bent in water and straight when out of it
The necks of doves appear different in colour depending on the angle of viewing
The same tower appears round from a distance, but square close at hand
If we press the side of an eyeball, objects appear a different shape
13. Knowledge Criteria / D. Scepticism / 6. Scepticism Critique
How can sceptics show there is no criterion? Weak without, contradiction with
13. Knowledge Criteria / E. Relativism / 1. Relativism
How can we judge between our impressions and those of other animals, when we ourselves are involved?
13. Knowledge Criteria / E. Relativism / 3. Subjectivism
Some actions seem shameful when sober but not when drunk
Sickness is perfectly natural to the sick, so their natural perceptions should carry some weight
Water that seems lukewarm can seem very hot on inflamed skin
If we had no hearing or sight, we would assume no sound or sight exists, so there may be unsensed qualities
If we enjoy different things, presumably we receive different impressions
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
Even if all known nations agree on a practice, there may be unknown nations which disagree
14. Science / A. Basis of Science / 1. Observation
How can you investigate without some preconception of your object?
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
15. Nature of Minds / C. Capacities of Minds / 6. Idealisation
If we try to conceive of a line with no breadth, it ceases to exist, and so has no length
17. Mind and Body / D. Property Dualism / 4. Emergentism
The incorporeal is not in the nature of body, and so could not emerge from it
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
18. Thought / D. Concepts / 2. Origin of Concepts / b. Empirical concepts
We can only dream of a winged man if we have experienced men and some winged thing
22. Metaethics / B. The Good / 1. Goodness / a. Form of the Good
Saying the good is useful or choiceworth or happiness-creating is not the good, but a feature of it
22. Metaethics / B. The Good / 1. Goodness / b. Types of good
Like a warming fire, what is good by nature should be good for everyone
22. Metaethics / B. The Good / 2. Happiness / d. Routes to happiness
If a desire is itself desirable, then we shouldn't desire it, as achieving it destroys it
23. Ethics / B. Contract Ethics / 9. Contractualism
Right actions, once done, are those with a reasonable justification
26. Natural Theory / A. Speculations on Nature / 4. Mathematical Nature
The tektraktys (1+2+3+4=10) is the 'fount of ever-flowing nature'
26. Natural Theory / C. Causation / 4. Naturalised causation
Some say that causes are physical, some say not
26. Natural Theory / C. Causation / 7. Eliminating causation
If there were no causes then everything would have been randomly produced by everything
Knowing an effect results from a cause means knowing that the cause belongs with the effect, which is circular
Cause can't exist before effect, or exist at the same time, so it doesn't exist
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
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?
If time and place are infinitely divided, it becomes impossible for movement ever to begin
If all atoms, times and places are the same, everything should move with equal velocity
A man walking backwards on a forwards-moving ship is moving in a fixed place
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?
27. Natural Reality / C. Space-Time / 2. Time / b. Tensed (A) time
Time doesn't end with the Universe, because tensed statements about destruction remain true
Time is divisible, into past, present and future
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
27. Natural Reality / C. Space-Time / 2. Time / f. Presentism
Socrates either dies when he exists (before his death) or when he doesn't (after his death)
If the present is just the limit of the past or the future, it can't exist because they don't exist
27. Natural Reality / C. Space-Time / 2. Time / i. Time and change
If motion and rest are abolished, so is time
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?
God must suffer to understand suffering
All men agree that God is blessed, imperishable, happy and good
28. God / A. Divine Nature / 3. Divine Perfections
The Divine must lack the virtues of continence and fortitude, because they are not needed
28. God / B. Proving God / 1. Proof of God
God is defended by agreement, order, absurdity of denying God, and refutations
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
God's sensations imply change, and hence perishing, which is absurd, so there is no such God
God without virtue is absurd, but God's virtues will be better than God
28. God / B. Proving God / 3. Proofs of Evidence / b. Teleological Proof
The original substance lacked motion or shape, and was given these by a cause
28. God / C. Attitudes to God / 4. God Reflects Humanity
The perfections of God were extrapolations from mankind
28. God / C. Attitudes to God / 5. Atheism
Gods were invented as watchers of people's secret actions
An incorporeal God could do nothing, and a bodily god would perish, so there is no God
29. Religion / A. Polytheistic Religion / 1. Animism
It is mad to think that what is useful to us, like lakes and rivers, are gods
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?