Self-study
Commentator: Many people argue that the release of chlorofluorocarbons into the atmosphere is harming humans by damaging the ozone layer, thus allowing increased amounts of ultraviolet radiation to reach Earth. ███ ███████ █████ ███ █ █████████ ███████ ███████ ███ █████ ██████ ████ ██ ███████████ ██████ ██ ███ ████████ ██████████ ███████ ███ ███████████ ██████████ ███ ████ ███████ ████ ███ █████████ ██████ ██ ███████████████████ ██████ █████ ██ ██ ██████ ██ █████ ████ █████ █████████ ██ ███ ██████████ ████ ██████ ██ ████ ████
Summarize Argument
The commentator concludes that there is no reason to think that chlorofluorocarbons (CFCs) in the atmosphere are harming humans by damaging the ozone layer and allowing excess ultraviolet (UV) radiation to reach Earth. As support, the commentator cites a supernova 300,000 years ago that damaged the ozone layer much more than CFCs are estimated to be damaging the ozone layer today. Since our earliest ancestors were not impacted by this damage 300,000 years ago, the commentator says that humans today won’t be harmed by the damage caused by CFCs.
Notable Assumptions
The commentator assumes that humans are similar enough to “our earliest ancestors” to conclude that something that didn’t damage our ancestors won’t damage us. The commentator also assumes that there have not been changes in the past 300,000 years that may augment the harm of a damaged ozone layer.
2.
Which one of the following, ██ █████ █████ ████ █████████ ██████ ███ █████████████ █████████
a
Extraterrestrial influences on ███ █████ █████ ████ ██ █████ ████ █████ ████ ███████████ █████
We don’t care about other influences on the ozone layer; the argument is specifically focused on whether or not damage to the ozone layer caused by CFCs will be harmful for humans. Furthermore, the quantity of these extraterrestrial influences definitely isn’t relevant.
b
Natural events, such ██ ███ ████████ ██ ██████████ ████████ ██ ██████ ███ █████ █████ ██████
Similar to (A), for this argument, we only care about the impact that CFCs have on the ozone layer; other influences on the ozone layer are irrelevant to the commentator’s argument.
c
Our earliest ancestors █████████ ███████ ███████████████ ██████ ████ ████ █████████ ████ ██ ███ ██ ███ ███████ ███████ ██ ███████████ ██████████
(C) widens the gap between the premises and conclusion. It’s great that our earliest ancestors weren’t harmed by the damage to the ozone layer, but if they were more resistant than we are to UV radiation, then we cannot use their experience as a basis for this claim about humans.
d
The ozone layer ███████████ ██ █ ████ █████ ███████ █████████████ ██████████
The argument is about damage to the ozone layer, not repairing the ozone layer, so this is outside of the scope of the argument. We don’t know if any counteractive processes are happening.
e
Scientists have discovered ████ ███████ ███████ ████████ ██ ███ █████████ ██████ ███ ██████ ██ █████ ███ █████████ ████████ ██████
This is too vague––without any indication of what kind of genetic changes occurred, this is not enough information to weaken the argument. It could be the case that all of these genetic changes are completely independent from reactions to UV radiation.