26 Exercise Answers
Philosophy 102 (Maher) Spring 2009
1. (a) p(E|H2 ) > p(E|H1 ) so, by the law of likelihood, E favors H2 over H1 . (b) p(H2 |E)/p(H1 |E) = 1 > 2/3 = p(H2 )/p(H1 ) so, by the denition of favoring, E favors H2 over H1 . (c) p(H1 |E)/p(H2 |E) = 5/4 = p(H1 )/p(H2 ) so, by the denition of favoring, E doesnt favor either hypothesis. (d) p(E|H1 ) > p(E|H2 ) so, by the law of likelihood, E favors H1 over H2 . (e) p(E|H1 ) = 0.2 > 1/6 = p(E|H2 ) so, by the law of likelihood, E favors H1 over H2 . (f) p(E|H1 ) = 1 = p(E|H2 ) so, by the law of likelihood, E doesnt favor either hypothesis. (g) p(E|H1 ) = 1 > 0.6 = p(E|H2 ) so, by the law of likelihood, E favors H1 over H2 . 2. (a) If N then species are formed by accumulating individual dierences. This will produce dierent varieties that gradually diverge until they are so dierent we count them as dierent species. But since the divergence is gradual, there will always be groups at intermediate stages. Hence p(E|N ) is high. If C then dierent species were created separately, whereas subspecies and varieties were not. This is a fundamental and dierence there is no apparent reason why it should be so dicult to detect. Hence p(E|C) is low. p(E|N ) > p(E|C) so, by the law of likelihood, E favors N over C. (b) If N then new species will be continually produced by natural selection. Thus p(E|N ) is high. If C then all species could have been produced at one time, or at several distinct times; there is no apparent reason for them to be produced continuously. Thus p(E|C) is low. p(E|N ) > p(E|C) so, by the law of likelihood, E favors N over C. (c) If N then the species on the same continent are likely to be descended from a common ancestor and hence related to one another. Also, species on dierent continents have been evolving in isolation from each other for a long time and hence are likely to dier. Hence p(E|N ) is high. If C then unrelated species could have been created on one continent, for example, where the conditions are dierent. Also, the same species could have been created on dierent continents where the conditions are the same. Hence p(E|C) is low. p(E|N ) > p(E|C) so, by the law of likelihood, E favors N over C.