Mapping an Argument: Claim, Reasons, Evidence

Break an argument into its working parts so you can evaluate each one.

Before you can judge an argument, you must see its structure. The claim is the main position the writer wants you to accept. Reasons explain why the claim should be accepted. Evidence, such as data, examples, expert testimony, or observations, supports each reason. Mapping these parts shows where an argument is strong and where it is thin. Worked example: 'Our school should start classes at 9:00 instead of 7:45. Teenagers' sleep cycles shift later during adolescence, so early starts cut into needed sleep.

A district that made this change reported fewer tardies and higher first-period grades the following year. ' Claim: start at 9:00. Reason: early starts deprive teens of sleep because of biological sleep shifts. Evidence: one district's results. The map immediately reveals a question: is one district enough? Without mapping, a reader tends to react to how convincing an argument feels. With a map, you can evaluate each part on its own merits.

• 1The claim is the position; reasons explain why.
• 2Evidence supports each reason.
• 3Mapping exposes where an argument is thin.