Drill #001: ad hominem
A columnist writes: The city council claims that installing bike lanes will reduce traffic congestion. But the council members who proposed the bike lanes all live downtown, where congestion is worst. They're just trying to make their own commutes easier. So we should reject their claim that bike lanes reduce congestion.
The columnist's reasoning is most vulnerable to criticism on the grounds that it
- treats a proposal that would benefit its proponents as therefore certain to benefit no one else
- rejects a claim by attacking the motives of those who advance it rather than the claim itselfCorrect
- presumes, without justification, that congestion downtown matters more than congestion elsewhere
- takes for granted that the council members agree about what causes congestion
- confuses a claim's being popular with its being true
The credited answer is B. The columnist rejects the council's claim by going after the members' motives (they want easier commutes) instead of the claim itself. That's an ad hominem: a claim can be true even when the people making it stand to gain. A is the trap, but the columnist never argues the lanes help no one else, he just dismisses the claim based on who made it.
Ad hominem is one of the patterns in the free LSAT cheat sheet.
