According to LSAC, the Logical Reasoning portion of the LSAT is designed to "evaluate the ability to analyze, critically evaluate, and complete arguments as they occur in ordinary language . . . These arguments mirror legal reasoning in the types of arguments presented and in their complexity, though few of the arguments actually have law as a subject matter."Read More
Most students confront conditional reasoning very early on in their LSAT preparation. They spend hours mastering the logic of conditional rules in Logical Reasoning stimuli and answer choices, and in Logic Games as well. To this end, students must memorize a number of common conditional reasoning keywords and phrases that help indicate the presence of this logic. Some of these indicators become incredibly obvious with practice. Many of us can recall a moment when, while working through a previously unseen logical reasoning question, we encounter the all-too-familiar "if....then" construction. With a gleam in our eye and a smile across our face, we confidently say to ourselves, "I've got this," and quickly draw out a perfect diagram of the rule.
But every so often there comes a moment when we see that familiar "if", and, just as our hearts start to warm with recognition, a specter looms on the horizon—standing menacingly in front our old friend "if" . . . the word "even". "Even if". Wait . . . what?Read More
In my previous blog post I talked about the basics of conditional reasoning on the LSAT, and dealt with fairly simple statements involving a single sufficient condition and a single necessary condition. You’ll find that post here:
On the LSAT, though, things are not always that simple! Sometimes (often, really) you will encounter conditional chains, where one thing is sufficient for another, which is sufficient for a third, which is sufficient for a fourth. Stringing these conditional claims together in the right order, and then knowing which conditions affect others and in what ways, will be crucial to your success. You will encounter chains in Must Be True questions, Parallel Reasoning, Parallel Flaw, Justify the Conclusion, and others. So, how do you manage to interpret the relationships correctly?
By playing with dominoes!Read More
Conditional reasoning – argumentation based on “if…then” statements – is a prominent feature of the LSAT. While the numbers vary from test to test and year to year, you can expect something in the neighborhood of 10 questions in the Logical Reasoning sections that involve conditional reasoning, and at least half of the Logic Games will employ it as well. Some games (typically undefined or partially defined grouping games) will be entirely conditional, with every single rule setting up an if…then statement (if R is on the committee, X is also on the committee; if W is not on the committee, S is on the committee; etc.). In short, while conditional reasoning is not the be-all and end-all of the LSAT, it is a subject that should be mastered if you want to do well on the test, and it therefore deserves attention and practice.Read More
Granted, most Logical Reasoning questions with conditional reasoning won’t require you to negate the conditional relationships in them. You will certainly need to know what the contrapositive is, and—if there are multiple conditional relationships—you need to know how to form a conclusion by combining them into a chain (aka the “law of syllogism”). Occasionally, in Justify questions, you will need to establish a logical link between the premises and the conclusion. And in Flaw questions, you will need to know how to describe in abstract terms the most common logical fallacies involving conditional reasoning.
A question that frequently comes up from readers of the LSAT Logical Reasoning Bible is, when should I diagram conditional statements in the LSAT Logical Reasoning section? In the book, I talk about diagramming in a number of different chapters, but most prominently in the chapter on Conditional Reasoning.
A student of ours who's working through the PowerScore Logical Reasoning Bible asked a common question the other day, and I want to share it, and my response, with you.
Specifically she's been struggling with Mistaken Negations and Mistaken Reversals in conditional reasoning, and asked if I could help her better understand those two errors.
Here's my reply:
On our LSAT Discussion Forum recently, I've been running into a recurrent question about a conditional reasoning rule. These questions revolve around a really tricky phrasing, one that has devastated test takers when it has appeared on previous LSATs. But if you can learn the idea, it takes something the test makers expect to be very difficult and turns it into something fairly easy. Plus, it's not that tough to learn! So what is this mysterious but critically important concept?Read More
Topics: LSAT Conditional Reasoning
The ability to logically negate a statement—whether conditional, causal, etc.—is critical to your success on the LSAT. It comes up most commonly in the Logical Reasoning section of the test, although any question stem using the word “EXCEPT” (always capitalized) will require you to logically negate that stem. The list does not stop here: every time you apply the contrapositive of a conditional statement, you will need to reverse and negate the two conditions that constitute that statement (this is relevant to Must Be True, Justify, and Parallel Reasoning questions mostly, but can also be critical in other sections of the test). Negating statements is also useful in Assumption questions, because proving the correct answer choice requires application of the Assumption Negation Technique: the correct answer choice, when logically negated, must weaken the conclusion of the argument. And, of course, the ability to understand the logical opposite of a conditional statement will be directly relevant to many Cannot Be True questions, where the correct answer choice is the one that can be disproven using the information contained in the stimulus.Read More
The other day I came across an apparently famous logic puzzle called The Wason Selection Task. I say "apparently" famous because I for one had never heard of it, but I was instantly struck by the conditional nature of the process in question.
If you're reading this I presume you've got some experience with LSAT conditionality—and if you'd like more I've included a number of helpful links at the end of this post!—so let's put your knowledge to the test.
Take a look at the picture up top, where four cards are arranged before you, two with numbers, and two with colors. What you're told of these four cards is that each of them has a positive, whole number on one side (two of which are exposed at the moment) and a color on the other (again, two of which are shown). So the 3 and the 8 have a colored back, and the red and the orange have a numbered back. Simple enough right?
Here's the question then. Of those four cards, which card(s) MUST be turned over to test the rule that "if a card has an even number on one side, then its other side is red"? Indicate only the card(s) needed (that is, with the potential) to determine whether that rule has been broken here.
Think you've got it?Read More