The two most important types of logic on the LSAT are conditional and causal reasoning.
Conditional reasoning may be dressed up in various guises, but can be essentially reduced to if-then statements. For example: “If you are a lawyer, then you must have passed the bar exam.”
If-then statements lead to powerful deductions. Every if-then statement has a valid contrapositive, such as: “If you did not pass the bar exam, you must not be a lawyer.”
Setting up the logic games in the analytical reasoning section of the LSAT often requires stringing together if-then statements with their contrapositives to find new deductions.
[Read: How to Set Up LSAT Logic Games.]
Many logical reasoning questions also require an understanding of conditional reasoning. Consider the earlier example: “If you are a lawyer, then you must have passed the bar exam.” If that statement was presented in a test question, one answer choice might say that if you passed the bar exam then you must be a lawyer. Is that true?
Not necessarily. Just because everyone who is a lawyer passed the bar exam does not mean that everyone who passed the bar exam is a lawyer. This is an example of flawed reasoning.
Conditional reasoning is so powerful and pivotal on the LSAT that many test – takers neglect other kinds of logic, particularly causal reasoning.
What Is Causal Reasoning?
Causal reasoning appears frequently on the LSAT, in both the reading comprehension and logical reasoning sections. Rather than if-then, it is composed of cause-effect statements. Examples include:
— I feel sick because I ate too much pasta.
— Law school applications went up due to the COVID-19 pandemic.
— Burning fossil fuels contributes to climate change.
Causal reasoning is critically important in law, science, social science, history and everyday life. However, unlike conditional reasoning, causal reasoning cannot be used to make logically valid deductions. All you can do with causal statements is strengthen or weaken them.
If the LSAT gives you a causal argument, it may ask you to find a flaw in it, or find evidence relevant to the validity of the argument, or identify ways to strengthen the argument, or compare the argument to other similar arguments. It will not ask you what must or must not be true based on it.
Identifying Causal Reasoning on the LSAT
A causal argument has two parts: a cause and an effect. The cause must occur before the effect. Before you dismiss this point as obvious, note that it is not necessarily true in conditional reasoning. Take the above conditional statement: “If you are a lawyer, then you must have passed the bar exam.” This is saying that if you are a lawyer, then you must have taken a bar exam in the past. It is not a causal argument.
While the cause must precede the effect in time, the order of the statement itself is irrelevant. Often the effect comes before the cause in a sentence, as in: “I feel sick because I ate too much pasta.” Here, the cause is eating too much pasta and the effect is feeling sick.
When in doubt, look for words associated with cause and effect. It helps that there are not too many ways to describe causal logic in the English language. Look for phrases like: “because of,” “contributed to,” “due to,” “responsible for,” “led to” and “produced by.”
Answering LSAT Causal Reasoning Questions
Once you have identified causal reasoning in a logical reasoning question or in a reading comprehension passage, your work is not over. It is easier, however.
Single out the cause and effect in the argument. Look for supporting evidence. Then determine what the question is asking you to do to the argument. Often, your task is to strengthen, weaken or evaluate the argument based on the evidence presented.
To weaken a causal argument, see if it mistakes correlation for causation. Just because you ate pasta and feel sick does not mean the pasta caused the illness. Perhaps something else is responsible, like the milkshake you drank, the roller coaster you rode or a stomach bug you caught.
To strengthen a causal argument, shore up the relationship between cause and effect. If everyone else who ate the pasta got sick, and none of those people drank a milkshake or came down with a stomach bug, then it probably was the pasta after all.
Just to be safe, however, be careful what you eat before getting on a roller coaster!
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