Non-Deductive Arguments

Here are the answers to the group work we did in class on args by example, args by analogy, args from authority, and args about causes. Conclusions are in bold.

1. That Honus Wagner baseball card shouldn’t be that valuable. After all, it’s made out of cardboard, and cardboard boxes at Pathmark are super cheap.

Analogy
Bad - Material isn't always a relevant similarity to draw a conclusion about value: baseball cards are typically valued for their rarity, not what they're made of.

2. Canada, Mexico, USA, India, and Australia are all countries that border oceans on the east and west. Hence, most countries border oceans on both the east and west.

Example
Bad - 5 countries out of about 200 total nations is too small a sample. Also, the examples are cherry-picked, and so they're unrepresentative.

3. In a recent study, 100% of those who took a new birth control pill didn’t get pregnant. Only males participated in the study. Thus, the birth control pill must be very effective.

Cause
Bad - A better explanation of the correlation between taking the pill and not getting pregnant is that males don't get pregnant.

4. Oasis sounds just like The Beatles. We all know that The Beatles were one of the most influential rock bands ever. So Oasis must be one of the most influential bands, too.

Analogy
Bad - A similar sound isn't a relevant enough similarity regarding whether a band is influential.

5. Abortion is morally acceptable because renowned linguist Noam Chomsky has defended the practice of abortion, and he’s pretty smart.

Authority
Bad - Chomsky's expertise (linguistics) isn't relevant to the topic of abortion.
(Chomsky explains his view on abortion in the video to the right.)

6. Most people say the money it costs to go to law school is worth it, because lawyers earn a lot of money. So, since doctors also earn a lot, med school costs must be worth it, too.

Analogy
Pretty Good - The similarity (average money earned per profession) is relevant to whether med school is financially worth it. Assuming one thinks a large up-front investment is worth an even larger salary in the future, this arg is good.

7. My friend knows me better than anyone else, and he says I’m a decent guy. Therefore, I must be a decent guy.

Authority
Bad - Yes, my friend is a relevant expert, but he's likely to be biased in favor of me since he is my friend.

8. My sis usually keeps her car windows rolled down, though she always rolls them up right before it rains. Her car must be magical, then: rolling up her windows causes it to rain.

Cause
Bad - This is reversed! The rain probably causes her to roll up her window, not the other way around.

9. This guitar-shaped flyswatter costs $2 more than that normal one. Most of the expensive stuff I’ve bought in the past turned out to be higher quality than similar, cheaper items. Hence, the guitar-shaped swatter is higher quality than the normal one.

Example
Bad - While there may be a general correlation between expense and quality, it is not representative of this kind of novelty item. There is also a correlation between price and novelty: the more unique an object is, the more expensive it typically is.

10. Nearly every time I see Conan O’Brien on television, I wind up falling asleep. Thus, I guess Conan puts me to sleep.
Cause
Bad - Another way to explain this correlation between Conan and my sleep is the fact that his shows have been on late at night, a time at which I'm usually tired anyway.