1. 1 T HOUGHT EXPERIMENT A RGUMENTS 1

2. 2 Thought experiments are devices of the imagination used to investigate the nature of reality (including physical, psychological, and social/ethical). They have been used in natural sciences, social sciences, history, mathematics, and philosophy. 2

3. W HY USE THOUGHT - EXPERIMENT ? Real experiments may be very time-consuming and expensive. Real experiments may be unethical. Real experiments may be physically impossible. 3

4. 4 ECONOMICS 4

5. 5 The demand-supply model is the product of thought experiment (rather than empirical studies). 5

6. 6 Based on this model, we can explain and predict the relation between price and quantity of a product (or the inflation rate and GDP of a country). 6

7. 7 PHYSICS 7

8. 8 Aristotle: the heavier a body is, the faster it falls. Galileo: all things fall with the same speed (or acceleration). 8

9. 99 A BA+B Galileo’s Thought Experiment

10. 10 Assume that Aristotle is right. B falls faster than A. How fast will (A+B) fall? Ans1: (A+B) will fall faster than B because (A+B) is heavier than B. Ans2: (A+B) will fall slower than B because A will act as a “brake” on B. Ans1 contradicts with Ans2. Therefore, Aristotle must be wrong. 10

11. 11 E THICS : C AUSAL RESPONSIBILITY 11

12. W HICH STATEMENT IS TRUE ? A person is morally responsible for an event because she is the cause of it. A person is the cause of an event because she is morally responsible for it. 12

13. 13 Suppose that a building is on fire and a fireman is asked what is the (primary) cause of the fire. His answer may include: a short circuit, someone’ having smoked on bed, an overheated transformer, etc. Under normal situation, his answer will NOT include the presence of oxygen. 13

14. 14 Although the presence of oxygen is a necessary cause, it is not a salient cause. When we are asked what causes an event, we are asked about the salient causes. In normal situations, either we have already known that the presence of oxygen causes fire or we are not interested in knowing this cause. Hence, what makes a cause a salient cause depends on our interest. 14

15. 15 When we ask who causes an event, we are interested in finding out who is morally responsible for the event. I.e., who is morally responsible for the event is the salient cause. We can use thought experiments to support this point. 15

16. 16 A THOUGHT EXPERIMENT Jack made a bomb parcel and mailed it at a post office. A postman delivered the parcel to Paul’s home. Paul opened the parcel and was blown up into pieces. Who caused Paul’s death? 16

17. 17 Jack, the postman, and Paul all are involved in the causal chain resulting in the death of Paul: If Paul had not opened the parcel, he would not have been killed. If the postman had not delivered the parcel, Paul would not have been killed. If Jack had not mailed the parcel, Paul would not have been killed. However, since only Jack is morally responsible for Paul’s death, we think that only he is the cause. 17

18. 18 A NOTHER THOUGHT EXPERIMENT Nancy and Jane work for the same company. They each need to use a central computer for work sometimes. The computer is very old. If two people are logged on at the same time, it usually crashes. 18

19. 19 The company has instituted a policy: Nancy would be the only one permitted to use the computer in the mornings; Jane would be the only one permitted to use the computer in the afternoons. One day Nancy logged on the computer at 9am. Jane disobeyed the policy and also logged on at 9am. The computer crashed immediately. Who caused the computer to crash? 19

20. 20 Both Nancy and Jane caused the computer to crash. The cause is a conjoint cause. We think Jane rather than Nancy caused the crashing because we think Jane acted wrongly. That is, Jane’s having acted wrongly renders her action a salient cause. 20

21. CONCLUSION A person is the (salient) cause of an event because he is morally responsible for it. 21

22. 22 E THICS : M ORAL PERMISSIBILITY 22

23. 23 DOES THE MORAL PERMISSIBILITY OF AN ACTION DEPEND ON CONSEQUENCES ONLY ? The Split Track Case Suppose a trolley is heading towards 6 people who are trapped on the main track. It is morally permissible to divert the trolley into a side track on which a person is trapped so that the six will be saved and the one will be killed. 23

24. 24 The Bridge Case It is morally impermissible to push a fat man from a bridge into the trolley in order to stop it from heading towards the 6 people. 24

25. Note that the consequences of this action are the same as those of redirecting the trolley in the Split Track Case. http://www.youtube.com/watch?v=6WB3Q5EF4Sg 25

26. E MPIRICAL RESULTS 26 Split Track CaseBridge Case Participants approving diverting the trolley 90%10%

27. C ONCLUSION The moral permissibility of an action depends on things other than consequences. What are they? 27

28. 2 POSSIBLE ANSWERS Intention Theory The moral permissibility of an action also depends on the action’s intention. Intending evil (i.e., intending to involve someone in an activity that is harmful to her) is wrong. In the Split Track case, the hit on the victim is only a side-effect; the agent does not intend the hit In the Bridge case, the agent intends the hit on the victim (the evil) as a means to save the five. Therefore, it is wrong to push the fat guy. 28

29. Causal Sequence Theory The moral permissibility of an action also depends on the causal relation of the action’s consequences. Assuming that an action results in more good than evil, it is still wrong if the evil causes the good. In the Split Track Case, the hit on the victim (the evil) is not causally necessary to save the five (the good). Therefore, diverting the trolley is not wrong. 29

30. In the Bridge Case, the hit on the victim causes the trolley to halt, and thereby saves the five. Therefore, pushing the fat guy is wrong. 30

31. WHICH THEORY IS TRUE? The moral permissibility of an action depends on its rationally expected consequences. Actions motivated by bad intention usually have bad expected consequences. Actions motivated by good intention usually have good expected consequences. Therefore, the permissibility of an action depends derivatively on it intention. This can be shown by the following thought- experiment. 31

32. 32 Thought experiment 1 Suppose that Andrew gave a peanut butter sandwich to a starving person and he died after eating the sandwich because he was allergic to peanuts. Scenario 1: Andrew believed that the starving person was allergic to peanuts and intended to kill him. Andrew’s action has good consequences only if he mistakenly believed that the starving person had the allergy. Thus, his action has bad expected consequences. Therefore, his action is wrong.

33. Scenario 2: Andrew did not know that anyone was allergic to peanuts, and his ignorance is not due to his fault. Andrew’s action has bad consequences only in rare cases. Thus, his action has good expected consequences. Therefore, his action is right. But we want to know whether the permissibility of an action depends fundamentally on its intention? In order to answer this question, we need to answer the following questions. 33

34. Q UESTION Some actions having good expected consequences can be motivated by bad intention. Are they wrong? 34

35. 35 Thought experiment 2 I give several coins to a charity-flag seller. My action has good expected consequences. However, my intention is to make her collection bag heavier so that she will find more difficult to carry the bag. Is my action wrong?

36. Q UESTION Some actions fulfilling the agent’s duties can be motivated by bad intentions. Are they wrong? 36

37. 37 Thought experiment 3 Your class presentation is poor. I inform you honestly. I am fulfilling the duty of a teacher. My intention is to humiliate and discourage you. Is my action wrong?

38. A C HALLENGE TO THE I NTENTION THEORY If the moral permissibility of an action depends on its intention, the same action may be permissible for A to do but impermissible for B to do. 38

39. 39 Thought experiment 4 A patient with painful terminal cancer requests a doctor to withdraw her respirator to let her die. Doctor A is willing to do so in order to prevent her from suffering unnecessarily. Doctor B is also willing to do so because he thinks that this patient is too annoying and is happy to get rid of her. If the permissibility of an action depends on its intention, we have to say that Doctor A is permissible to withdraw the patient’s respirator but Doctor B is not.

40. A C HALLENGE TO THE C AUSAL SEQUENCE THEORY Intention is intuitively morally relevant, but casual sequence of action’s consequences is not. We need to ask why causal sequence is relevant to whether an action is morally permissible or not. 40

41. CONCLUSION We still do not which theory is correct. 41