Chp 9 Inference to Best Explanation PDF

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Chp 9 Inference to Best Explanation Many explanations are grounded in

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I am wearing a cast because I broke my arm

.

Sometimes, we want to give an explanation when no direct observations are available.

E.g. Say that your car won’t start and you want to know why. My car won’t start because the spark plugs are malfunctioning. Here, a

has been

The

in order to

is now subject to

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Hypothetical reasoning involves four basic stages: 1. . car won’t start. 2. The car won’t start because the spark plugs are malfunctioning. 3. s. The spark plugs will be dirty. Replacing the spark plugs will fix the problem. 4. but added to the evidence. A hypothesis is a free creation of the mind used to structure the evidence and unveil the pattern that lies beneath the surface. A hypothesis directs the search for evidence, telling the investigator what evidence to look for and what to ignore. If the implications are confirmed this does not prove the hypothesis to be true. 

If H then I. I Thus, H Fallacy of Invalid

If H then I. not I Thus, not H. The situation is actually a bit more complicated.

What are we doing when we confirm the implication? Inductive argument Popper – science should be falsified What are we doing when we test a hypothesis?

Duhem-Quine Thesis: It is impossible to test a hypothesis in isolation.

Inference to the Best Explanation The car won’t start. In order to start, a car needs clean spark plugs. The spark plugs must be dirty. To be the BEST explanation we need to confirm the hypothesis or try eliminate all other hypotheses. How can we judge whether or not a hypothesis/theory should be accepted (before it can be confirmed)? Must be consistent. Internally consistent - theory must be free of contradictions Externally consistent - must be consistent with the data that it is to explain Internal Consistency - Galileo showed that Aristotle’s theory of motion implied a contradiction External Consistency - E.g. Find round hole in broken windshield with blood on the dash and a brick on the front seat. Hypothesis - a brick must have been thrown through the window How can we judge whether or not a hypothesis/theory should be accepted (before it can be confirmed)? The best theory will meet the criteria of adequacy better than its competitors. Testability Fruitfulness Scope Simplicity Conservatism Testability Some way to test whether the theory is true or false. Moral Fault of Disease – immoral behaviour causes illness Chinese Medicine – health problems are caused by an imbalance in a person’s chi (an unmeasurable form of mystic energy) Testable if the theory predicts something other than what it was introduced to explain and this can be checked. Fruitfulness Does the theory suggest new insights or open up new areas of research?

E.g. Einstein’s special relativity – time slows down as you travel faster Scope Does the theory explain diverse phenomena? Before Galileo people thought that the laws of the heavens were different from the laws on the Earth. Galileo showed that motion in the heavens and on Earth are governed by the same gravitational law. Simplicity The best theory will be the one that makes the fewest assumptions. Why should we expect nature to be simple? Force + Gorce = mass x acceleration Ad hoc hypothesis – cannot be verified independently of the phenomena it is supposed to explain. Conservatism Does the theory require us to abandon any well-held beliefs? Perpetual motion machine Violates law of thermodynamics – mass-energy cannot be created or destroyed. Phenomenon: the construction of the Eqyptian pyramids Theories: (1) work of clever Egyptian engineers and many slaves, (2) the work of Egyptians with the help of extraterrestrial beings, (3) the work of the ancient Romans Testable – other phenomena to be checked Fruitfulness – new insights Scope – explain variety of phenomena Simplicity – makes few assumptions Conservatism – don’t need to abandon beliefs...