Truth and Probability Ayer, ch 5

1
Truth and ProbabilityAyer, ch 5

• September 19, 2008

2
I. Holism

• When one speaks of hypotheses being verified in
  experience, it is important to bear in mind that
  it is never just a single hypothesis which an
  observation confirms or discredits, but always a
  system of hypotheses. Ayer, p.94

3
1. The speed of light is effected by the
ether. 2. The unimpeded speed of light is
constant no matter which direction it travels. 3.
The ether flows opposite the direction of
rotation of the earth. 4. When light travels 100m
perpendicular to the earths rotation it takes n
seconds. 5. When light travels 100m parallel to
the earths rotation it takes n seconds. 6. Our
measuring device is accurate. 6.1 We can
accurately measure 100m in different
directions. 6.2. We can accurately measure n
seconds at different times. 9. We observed the
outcome correctly.
4
1. The speed of light is effected by the
ether. 2. The unimpeded speed of light is
constant no matter which direction it travels. 3.
The ether flows opposite the direction of
rotation of the earth. 4. When light travels 100m
perpendicular to the earths rotation it takes n
seconds. 5. When light travels 100m parallel to
the earths rotation it takes n seconds. 6. Our
measuring device is accurate. 6.1 We can
accurately measure 100m in different
directions. 6.2. We can accurately measure n
seconds at different times. 9. We observed the
outcome correctly.
1, 2, 3, 4, 5, 6, 7, 8, 9
5
I. Holism

• It appears, then, that the facts of experience
  can never compel us to abandon a hypothesis.
  Ayer, p.95

6
1. The speed of light is effected by the
ether. 2. The unimpeded speed of light is
constant no matter which direction it travels. 3.
The ether flows opposite the direction of
rotation of the earth. 4. When light travels 100m
perpendicular to the earths rotation it takes n
seconds. 5. When light travels 100m parallel to
the earths rotation it takes n seconds. 6. Our
measuring device is accurate. 6.1 We can
accurately measure 100m in different
directions. 6.2. We can accurately measure n
seconds at different times. 9. We observed the
outcome correctly.
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
10. P and not P is always false. 11. The
relevant inference rules that tell us that 1-9
entails P and not P.
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I. Holism

• Re-evaluation of some statements entails
  re-evaluation of others, because of their logical
  interconnectionsthe logical laws being in turn
  simply certain further statements of the system,
  certain further elements of the fieldBut the
  total field is so underdetermined by its boundary
  conditions, experience, that there is much
  latitude of choice as to what statements to
  re-evaluate in the light of any single contrary
  experienceAny statement can be held true come
  what may, if we make drastic enough adjustments
  elsewhere in the system. Quine, Two Dogmas
  p.39-40

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II. Science and Holism

• What are the considerations that determine in
  any given situation which of the relevant
  hypotheses shall be preserved and which shall be
  abandoned? Ayer, p.97

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II. Science and Holism

• Option 1
• Science obeys a principle of economy. Preserve
  the most hypotheses possible.

10
II. Science and Holism

• Option 2
• Science aims for successful prediction.
• What guides scientific theory choice?
• Consistency
• Ability to make useful prediction

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II. Science and Holism

• Q Is the only aim of science prediction?
• What about explanation?

12
II. Science and Holism

• Prediction/Explanation sometimes go together
• Tracking Hurricanes.
•  
• Prediction/Explanation often come apart
• Farmers Almanac.
• Sailors Adage.
• Flagpole and shadow.