Self-study
Support Every brick house on River Street has a front yard. ████ ██ ███ ██████ ██ █████ ██████ ████ ████ █████ █████ ████ ████ ███ ████████ ██ ████ ██ ███ █████ ██████ ██ █████ ██████ ████ ███ ████████
Method of Reasoning
The argument presents a conditional statement (if you’re a brick house on River Street, you have a front yard), connects it to a “most” statement (most houses on River Street with a front yard also have two stories), and then draws a conclusion (most of the brick houses on River Street have two stories).
Identify and Describe Flaw
This argument is flawed because it employs an invalid argument form. When a necessary condition of a sufficient condition is linked to a “most” statement, you’re not able to draw a connection between the sufficient condition and the most statement linked to the necessary condition (as diagrammed above). Just because all brick houses on River Street have front yards, and most houses on River Street with front yards have two stories, that doesn’t necessarily mean that most of the brick houses on River Street have two stories. It’s entirely possible that only some or even none of the brick houses on River Street have two stories.
23.
Which one of the following ██ ████ ███████████ ██ ██ ███████ █████████████ ████ ███ █████████ ██ ███ ████████ █████ ██ ███████
a
By that line ██ ██████████ ██ █████ ████████ ████ ████ ███████████ ████ ███ ███ ███████ █████ ███ ███████████ ███ ███████████ ███ ████ ███████████ ████ ███ ███ ███████
Wrong flaw. If all legislators are politicians, and most legislators have run for office, we can infer that some politicians have run for office. However, we can’t infer a “most” statement from these conditional relationships. The stimulus, meanwhile, is flawed because when a necessary condition of a sufficient condition is linked to a “most” statement, you’re not able to draw a connection between the sufficient condition and the most statement linked to the necessary condition.
b
By that line ██ ██████████ ██ █████ ████████ ████ ████ ██████ ████████ ███ ████████████ █████ ████ ███████████ ████ ███ ███ ██████ ███ ████ ███████████ ███ ████ ███ ███ ██████ ███ ██████ █████████
Wrong flaw. (B) presents a “most” statement (most legislators have run for office), connects it to another “most” statement (most politicians who have run for office, which is a group that includes all legislators, are public servants), and erroneously infers that most public servants are legislators, which is an invalid argument form. The stimulus, meanwhile, doesn’t try to draw a conclusion from two “most” statements.
c
By that line ██ ██████████ ██ █████ ████████ ████ ███ █████ ██████ ███████ ███ ███ ███ ███████ █████ █████ ██████████ ██ █ ██████ ███████ ███ ████ ██████ ████████ ███ ███ ████████████
Wrong flaw. (C) is flawed because it introduces an idea in its conclusion (running for office) that isn’t even discussed in its premises. The stimulus, on the other hand, doesn’t introduce a totally new concept in its conclusion.
d
By that line ██ ██████████ ██ █████ ████████ ████ ████ ███████████ ████ █████ ███ ███ ███████ █████ ████ ██████ ████████ ████ █████ ███ ███ ██████ ███ ███ ███████████ ███ ██████ █████████
The argument presents a conditional statement (if you’re a legislator, you’re also a public servant), connects it to a “most” statement (most public servants have never run for office), and then draws a conclusion (most legislators have never run for office). This commits the same flaw as the stimulus of when a necessary condition of a sufficient condition is linked to a “most” statement, you’re not able to draw a connection between the sufficient condition and the most statement linked to the necessary condition (as diagrammed below).
e
By that line ██ ██████████ ██ █████ ████████ ████ ████ ███████████ ███ ███ ██████ █████████ █████ ████ ██████ ████████ ████ ███ ███ ███ ██████ ███ ████ ███████████ ████ ███ ███ ███████
Wrong flaw. (E) presents a “most” statement (most public servants have not run for office), presents a totally separate “most” statement (most legislators have run for office), and erroneously draws a conclusion based on the unconnected “most” statements (most legislators are not public servants). When two “most” statements have nothing to do with each other, you can’t make any inferences about them. The stimulus, meanwhile, doesn’t present two “most” statements.