Analyze reasoning (cause, analogy, generalization) and detect weak support.
Test whether the reasoning really supports the conclusion or leaves a gap.
Core Idea
When an author moves from evidence to explanation, check the kind of reasoning being used. A causal claim, analogy, or generalization is only as strong as the link between the evidence and the conclusion.
Understanding
Natural-science passages can sound convincing because they include technical detail, but ACT Reading still asks the same question: does the evidence actually prove the claim? If the author argues that one factor caused another, test an alternative cause. If the author generalizes from a limited set of observations, ask whether the leap is too broad.
Weak support often appears when the passage treats timing as proof of cause, treats a small sample as if it represents a whole system, or treats a surface similarity as if it justifies a larger conclusion. Your job is to find the gap between the evidence and the claim, not just a detail that sounds negative.
Step by Step
- Name the reasoning pattern the author is using.
- Locate the exact conclusion, not just the topic.
- Ask what other explanation could fit the evidence.
- Choose the answer that most directly exposes a gap between the evidence and the claim.
Misconceptions
- If two events occur together, one must have caused the other.
- Scientific vocabulary automatically means the reasoning is strong.
- A few observations can safely stand in for a broader pattern.
Worked Example
A natural science passage notes that a marsh's water became clearer during the same two summers in which dragonflies returned in large numbers. The author concludes that the dragonflies caused the change in water clarity. Which statement, if true, would most weaken the author's conclusion?
Select an answer to see the explanation