December 2000 LSAT Section 1 Question 11
Researchers have discovered that caffeine can be as physically addictive as other psychoactive substances. Some peop...
1 Reply

Melody on December 29, 2014
The argument states "researchers have discovered that caffeine can be as physically addictive as other psychoactive substances."As you have pointed out, "caffeine" has not directly been defined as a psychoactive drug, but does that mean it is not one? The argument does not explicitly state what type of drug caffeine is. Therefore, it could still logically be a psychoactive drug.
Further, we are implicitly told that "caffeine" is a psychoactive drug.
The last sentence states: "as many people consume caffeine as consume any one of the other addictive psychoactive substances." Saying "any one of the other," implies that there are "other" addictive psychoactive substances other than caffeine--this implicitly includes caffeine as a part of the overarching group of addictive psychoactive substances.
So, for these reasons, we cannot logically conclude that "not all." i.e. at least one, "substances to which people can become physically addicted are psychoactive."
Whereas, we have been explicitly told that an equal amount of people consume caffeine" as those who consumer any other addictive psychoactive substances."
So, the argument tells us that there is no physically addictive psychoactive substance that is consumed more than caffeine is, i.e. answer choice (E).
Hope that clears things up! Please let us know if you have any other questions.