In the Formal Logic chapter, you learned things like If A = B and B = C, then A = C. In real life and on the LSAT, most arguments aren’t that precise. They have assumptions that are hidden premises. This informal logic compromises most of the logical reasoning questions. Over the next few chapters, we’ll review informal logic. These chapters are organized by the question types rather than by specific topics. We’ll start by covering Main Idea questions, which ask you to identify conclusions.
These are statements that support a conclusion. They are like evidence.
- Due to…
- Studies have shown…
- As indicated…
- Given that…
- This can be seen from…
While the conclusion and the premises are stated in the argument, assumptions are not. On the LSAT, it’s a crucial skill to be able to identify any assumptions, or gaps, between the evidence and the conclusion.
Assumptions have no indicator words because they are unstated.
You may be asked to identify the conclusion, strengthen it, weaken it, identify why the reasoning in the argument is flawed, or find an answer choice with parallel reasoning to the argument to reach the conclusion.
- For this reason,…
No one ever said the LSAT was an easy test; don’t expect the test writers to make it as simple as described above. Expect patterns such as Premise + Premise = Sub-Conclusion + Premise = Conclusion.
CHALLENGE: Identify the Conclusion
The first thing to know is that Main Idea questions are different from summarize the above argument questions or restate the facts questions; they’re find the conclusion questions.
Main Idea questions are focused on finding the conclusion and are easily identifiable. These questions are typically phrased like this:
- The main point of the passage is that . . .
- Which of the following statements about . . . is best supported by the statements above?
- Which of the following best states the author’s conclusion in the passage above?
- Which of the following conclusions can most properly be drawn if the statements above are true?
- Which of the following completes the argument above?
How to Solve:
- Read and Understand the Passage: Be very precise in what each sentence means and what it doesn’t mean. Also, try to see how the sentences are inter-related.
- Predict a possible conclusion: Before looking at the option statements, try to think of possible statements that you can infer from the passage. Doing so will significantly increase your understanding of the passage.
- Evaluate Option Statements: Read and understand the option statements. Eliminate four option statements for solid reasons and accept one that you think is correct.
- Identify the premises and the conclusion: The answer is the conclusion.
- Avoid trap choices: Main Idea questions typically will have notably devious trap answer choices.
a) Avoid answer choices that are true, but aren’t the Main Idea.
b) Don’t pick a premise of the argument. A trap choice will often just restate facts.
Intro (0:01) | Ex.1 (2:35) | Ex.2 (6:45) | Ex.3 (9:55) | Ex.4 (12:51) | Ex.5 (16:49) | Trap Choices (20:54)
Next LSAT: July 11th
Everything in the argument that isn’t some type of conclusion can be classified as evidence. Evidence is important to identify because on the LSAT it is always true (“agree/disagree” questions are an exception). You will never get a correct answer by negating, arguing with, or contradicting the premises of the stimulus.
The conclusion, on the other hand, may be more or less plausible based on the evidence given. Its validity depends completely on how well it is supported by the evidence. You may be asked to identify the conclusion, strengthen it, weaken it, identify why the reasoning in the argument is flawed, or find an answer choice with parallel reasoning to the stimulus. More detailed information on LR question types can be found later in this chapter.
- Main idea questions go beyond Must be True because they are supported by other things in the argument (not a premise but a conclusion). Things that are just facts are premises, not conclusions.
- Premises are trick answer choices on Main Idea questions.
- The answer in a Main Idea question often relates to what the author is persuasively promoting.
- Main Ideas are sometimes unstated (implied).
- Stated conclusions are often stuffed in the middle of the stimulus and in a convoluted sentence (to make the question harder). Putting the Main Idea at the end of the stimulus would be just too easy.
Although Locke has been hailed as a giant figure in European intellectual history, his ideas were largely borrowed from his predecessors, who are now unfairly neglected by historians. Furthermore, Locke never wrote a truly great book; his most widely known works are muddy in style, awkwardly constructed, and often self-contradictory.
Which of the following represents the main idea of the passage?
- Locke made use of ideas without acknowledging his predecessors as the sources of those ideas.
- Current historians are re-evaluating the work of Locke in the light of present-day knowledge.
- Locke’s contributions to the development of European thought have been greatly exaggerated.
- Historians should reexamine Locke’s place in European intellectual history.
- Although Locke’s ideas were important, his way of expressing them in writing was sadly inadequate.
The author makes two assertions about Locke. First, his ideas were not original. Second, his books were not very good. Based on these assertions, the author concludes that Locke’s reputation as an intellectual giant is undeserved. Choice (C) accurately summarizes this conclusion.
- The focus is on a subsidiary point, not the main idea; moreover, it makes an assumption unsupported by the passage: that Locke did not acknowledge the sources of his ideas.
- It is wrong because although the passage clearly indicates that the author is “re-evaluating” Locke’s work, it does not suggest that “current historians” in general are doing so.
- This choice best expresses the point that Locke’s contributions were not original.
- This option is tricky because it is a good answer, but it is not the best answer. (D) implies that the author recommends that other historians re-examine Locke. Since no recommendation exists in the argument, choice (C) is the only option.
- Not addressed.
Next LSAT: July 11th