Ideas of Sextus Empiricus, by Theme

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

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1. Philosophy / F. Analytic Philosophy / 5. Against Analysis
You cannot divide anything into many parts, because after the first division you are no longer dividing the original
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 / A. Overview of Logic / 1. Overview of Logic
If we utter three steps of a logical argument, they never exist together
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
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 / D. Empiricism / 3. Pragmatism
We distinguish ambiguities by seeing what is useful
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 / 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
If we press the side of an eyeball, objects appear a different shape
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
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
If we enjoy different things, presumably we receive different impressions
If we had no hearing or sight, we would assume no sound or sight exists, so there may be unsensed qualities
Sickness is perfectly natural to the sick, so their natural perceptions should carry some weight
Some actions seem shameful when sober but not when drunk
Water that seems lukewarm can seem very hot on inflamed skin
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
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
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 / 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 / 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?
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
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?