LSAT Inference Questions

Sometimes, LSAT Test Day can feel as if you’re tasked with reading the mind of the author of a Logical Reasoning (LR) stimulus or Reading Comprehension (RC) passage. For example, on a practice LSAT you will see an RC question worded in this way: “With which of the following would the author be most likely to agree?” In LR, it may seem no different, with question stems that read “Which of the following most strongly supports the statements above?”
In such questions, the LSAT seems to be demanding the impossible—to guess at an infinite number of possible directions in which the author’s statements/passage might lead.
Instead of guess work, your job with Logical Reasoning and Reading Comprehension inference questions is detective work—which is not too different from making a deduction in Logic Games (LGs).
For instance, you will often see two paired rules in LGs—something like the following:

If Robins are in the forest, then Orioles are not.
If Orioles are not in the forest, then Robins are.

Initially, the two rules seem identical. But look more closely, like Sherlock Holmes would. In the first rule, the presence of Robins triggers the absence of Orioles. Contrapose that, and we see that If Orioles are in the forest, then Robins are not, as well. Here, in this first rule, the presence of one of the bird species triggers the absence of the other.
But we know nothing about what the absence of either bird species brings about. Add in the second rule above, and voilá! We now know that the absence of either bird species demands the presence of the other.
Even though the two rules don’t say it explicitly, we can deduce that this game will always require the presence of Robins or Orioles, but not both.
Making inferences in Logical Reasoning and Reading Comprehension demands the same skills as solving the LG deductive reasoning question outlined above. LR stimuli require us to put two or more statements together in order to know that a claim must be true or is strongly supported. Similarly, RC inference questions require us to combine statements that an author has made in the passage—statements that, when combined, lead overwhelmingly to a conclusion.
LR inference questions break into two types:

  • Must-be-true
  • Strongly-supported-by

Must-be-true inferences in Logical Reasoning

Must-be-true LR inference question stems literally use the words “must be true,” as in “Which of the following must be true based on the above information?” Approach must-be-trues like the following example. These three statements, when combined, lead to a conclusion that has to be true (but that is not explicitly stated):

  1. Randy never goes picnicking when it rains.
  2. The forecast shows a 100 percent chance of rain today.
  3. Out the window, it’s coming down in buckets.

What has to be true (but which is not stated in words) is that, given the three statements, Randy will not go picnicking today.
Might Randy stay inside and read a book? Possibly. Might he go out to get his mail? Maybe. Will he go picnicking with an umbrella? Absolutely not, because Randy never goes picnicking when it rains, and it is raining today.

Strongly-supported inferences in Logical Reasoning

Strongly-supported LR Inference questions operate slightly differently, and their question stems literally employ keywords “follows logically” or “strongly supported by,” as in “Which of the following most strongly supports the statements made above?”
For example:
Randy enjoys Italian food because he associates red sauce and ricotta cheese with previous family get-togethers that featured his Nana’s homemade stuffed shells. Though Randy has never had stuffed manicotti, it, too, features red sauce and ricotta cheese.
The strongly supported inference here is that Randy will enjoy manicotti in the same way he enjoys shells. Note that this is not a “must-be-true” situation. For all you know, Randy’s Nana may throw a violent fit at the thought of serving manicotti because of the one time she ate manicotti and got violently ill; she may have passed that phobia onto Randy. (And now you know more about Randy’s Italian family get-togethers than you ever wanted!)
However, only one answer choice will be the inference or deduction that is strongly supported by the stimulus statements: in this case, that Randy will like manicotti much in the same way he does shells.

Reading Comprehension inference questions

Although RC Inference questions don’t divide up in the same way (must-be-true vs. strongly-supported-by), you still make a valid inference on the basis of what has been said, leading to that which must be true or that which is strongly supported by the information in the passage.
For example, across the paragraphs of a Natural Science RC passage, the author lists all the means by which the creosote bush dominates its ecosphere:

  • Hard skin, resistant to the mandibles of insect predators
  • Toxic, foul-tasting resins that discourage predatory foraging
  • Sharp thorns
  • Overhanging branches that drop close to the ground and block sunlight penetration, lessening the growth of rival plants in its vicinity

Unless the passage tells us otherwise, we can safely infer that, even though not explicitly mentioned in the passage, locust plagues do not pose a threat to the creosote bush, nor do encroaching ground-cover plants. Why? The author has outlined in detail the creosote bush’s natural defenses, all of which rebuff the threats posed by locusts (mandibles, foraging) and ground-cover plants (encroachment).
Just like the Robins and Orioles, we put together what the author has explicitly stated in order to arrive at what must be true (or is strongly supported) on the basis of what she has stated.

Learning the skills to combine statements is, unlike the creosote bush, an acquired taste. You need to prep daily on LR and RC inference questions to recognize the tell-tale clues that imply what must be true or is strongly supported. After all, Sherlock Holmes did not have superhuman powers; he trained himself to recognize the clues that indicate the presence of what others cannot see—exactly the skill needed by lawyers to see in the law what others cannot see.