Scientific Inference

Question 1

Inference

Answer 1

the act or process of reaching a conclusion about something from known facts or evidence

Premise -> inference -> conclusion

Question 2

Direct inference

Answer 2

Observe 33% red in sample -> 33% red in population.

Question 3

Projection interference

Answer 3

Observe 9 red -> next observed will also be red

Question 4

Generalisation interference

Answer 4

Observe 9 red -> claim all are red.

Question 5

Modus Ponens

Answer 5

Method of affirming. If A1…An then T (accepting T if A)

Question 6

Modus Tollens

Answer 6

Method of denying. If H, then C. C is false -> H is false.

Question 7

Inductive inference rules

Answer 7

Direct, projection and generalisation

Amplify knowledge: extend conclusions beyond knowledge we already have

Conclusions from good inductive inferences and true premises are fallible – they might be false

Question 8

Deductive inference rules

Answer 8

Modus Ponens, Modus Tollens

Explicate knowledge: order and rearrange our knowledge without adding to its content

Conclusions from good (“valid”) deductive inferences and true premises are necessarily true

Question 9

Hume’s Problem of Induction

Answer 9

No inductive inference rule can be justified

1. Every inference is either an induction or a deduction
2. To justify an inductive inference rule I, this rule itself has to be inferred from some premises
3. I cannot be inferred deductively, because there are no necessary connection between past and future inferences
4. Thus, I must be inferred inductively
5. When inferring I inductively, we must appeal to another (inductive) inference rule J to justify this induction. But that raises the issue of how to justify J, which would require appealing to another inference rule K, …..

Question 10

Scientific Instrumentalism

Answer 10

Theories only order sets of observation reports - they might be helpful or not, but they are not true or false

Question 11

Hypothetico-Deductive Method

Answer 11

1. Formulate a hypothesis H
2. Deduce observable consequences {Ci} from H.
3. Test whether {Ci} is true or not.
4. If {Ci} is false, infer that H is false.
5. If {Ci} is true, increase confidence in H

Question 12

Good hypotheses

Answer 12

• A statement that can be either true or false
• A statement that is not necessarily true or false
• A statement that either has some generality (e.g. “all X in domain D…”), or that is about some unobservable (exclude statements like “this table is red”)

Question 13

Falsifiability

Answer 13

Quality of a hypothesis: A good hypothesis has more observable consequences that sets it apart from rival hypothesis.

Question 14

Falsification

Answer 14

An event - the observation that an implication of a hypothesis is not true, which by modus tollens then implies the falsity of the hypothesis.

Question 15

Popper’s Falsificationism

Answer 15

• Conjecture falsifiable hypotheses
• Seek to falsify these hypotheses with observable evidence
• Reject any falsified hypothesis as false
• Never accept any hypothesis as true – only maintain non-falsified hypotheses as so far not rejected

Question 16

Duhem-Quine Thesis

Answer 16

• We never test a single hypothesis alone, but only in conjunction with various auxiliary hypotheses.
• For falsifying the hypothesis: be confident that it’s not the auxiliary hypotheses responsible for falsity of the consequence
• No asymmetry between falsification and confirmation!

Question 17

ad hoc hypothesis

Answer 17

A hypothesis added to a theory in order to save it from being falsified.

Question 18

A modification is ad hoc if

Answer 18

it reduces the falsifiability of the hypotheses in question