Philosophy 210 - Logical Thought

Possible Midterm Answers

October 25, 2002

1. Because 'beans cause tumors' is a reason for claiming that beans (but not carrots) are unhealthful, the first sentence ('beans and carrots are unhealthful") must be split into two claims. By contrast, the claim that meat promotes good teeth applies equally to beef and lamb; so the first sentence of argument (b), "lamb and beef are so healthful" does not need to be divided. Hence there needs to be one more claim in (a) than in (b).

2.

3. (a) Violent people convert only to violent religions. (Or, snipers convert only to violent religions.) [Note that "Snipers convert to violent religions" is not quite right. First, they might convert to two religion, one that is violent and one that is not. Second, to make the argument sound, it is not necessary that snipers all convert to a religion; just that if they do, they convert to a violent one.]

(b) Strengthening gun laws is the best way to stop gun-related deaths. [Note that it is too much to say that it is the only way, since there might be other, but inferior, ways. And it is too little to say that strengthening gun laws will stop the deaths. That might work but work less effectively than some other way.

4. (a) "x[Dx ® "y(Txy ® –Ryx)]

(b) "x($y(–Ryx & Txy) ® Dx (equivalently "x[–Dx ® "y(Txy ® Ryx)]

another (non-equivalent) reading that was worth full credit was: "x["y(–Ryx ® Txy) ® Dx]

5.

	(A)	(B)
Arg 1	X	√
Arg 2	√	X
Arg 3	√	√