PHIL
1500 - Critical Thinking
Unit 3: Defeasible Reasoning
Dr. Donald Nute
Construct inheritance nets using the following information. Do not add any information
to that given in each example. Put a + next to the nodes indicated, then put
+, -, or ? next to all the other nodes.
1. (N)othos(+) are (K)illifish. Killifish and (R)ice fish are
(T)op minnows. Nothos normally lay their eggs in (M)ud. Top minnows normally
do not lay their eggs in mud.
2. Technically, a (P)orpoise(+) is a kind of (W)hale, and whales
are (M)ammals. Porpoises live in the (S)ea and the typical creature that lives
in the sea is not a mammal.
3. Of course, both (R)oyal(+) elephants and (A)frican(+) elephants are (E)lephants. (E)lephants are normally (G)ray, but royal elephants typically are not gray.
4. (W)hales(+) are (M)ammals and mammals normally (B)reathe air. Whales are
also (S)ea-creatures and sea-creatures normally do not breathe air.
5. Same as 4, but add the information that whales normally breathe air and that
(H)umpbacks are whales. Then start with + beside humpback.
6.(D)extrocephaloids(+) are normally (S)apioglutes and (M)alpeds(+)
normally are not. (E)upeds and malpeds are (H)ypercorticals. Eupeds are normally
(N)otopods, but hypercorticals are normally dextrocephaloids.
7. (B)ats(+) are (M)ammals, but animals that (F)ly normally are
not mammals. Bats are animals that fly.
8. (C)onservatives(+) are normally (R)epublicans and Republicans
normally are not (P)acifists. (S)upporters(+) of the Dukakis campaign normally
are not Republicans. Typically, (Q)uakers(+) are pacifists.
9. People who (S)top smoking typically (E)at more. People who
(C)ontract emphysema(+) due to smoking normally stop smoking but they don't
normally (G)aining weight. People who eat more usually gain weight.
10. (R)hodes Scholars(+) and college (G)ymnasts are college (A)thletes. Rhodes Scholars normally are not required to attend regular team (P)ractices. College athletes normally (R)eceive athletic scholarships, and students on athletic scholarships normally are required to attend regular team practices.
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