Logic Reasoning Flashcards
7 cards from real LSAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Logic Reasoning flashcards as text
A judge instructs: 'If new evidence is presented, the case will be reopened. The case was not reopened.' What can be concluded?
Answer: No new evidence was presented.
Applying modus tollens: the case was not reopened (consequent false), so no new evidence was presented (antecedent false).
The argument 'We should legalize marijuana because prohibition has failed, just as alcohol prohibition failed in the 1920s' relies primarily on which reasoning technique?
Answer: Analogical reasoning between two historical cases.
The argument draws a parallel between two historical prohibition situations, inferring that what happened with alcohol will apply to marijuana.
Which of the following, if true, most strengthens the argument that mandatory sentencing laws reduce violent crime?
Answer: Violent crime rates fell in states with mandatory sentencing but remained flat in comparable states without such laws.
A controlled comparison showing crime fell under mandatory sentencing but not without it provides direct causal evidence for the claim.
A scientist argues: 'This new species must be carnivorous because it has sharp teeth, and all previously discovered members of its genus are carnivorous.' This is an example of:
Answer: An inductively strong argument whose conclusion is probable but not certain.
The conclusion is supported by genus-wide patterns and anatomical evidence, making it inductively strong but not deductively certain since exceptions are possible.
Which flaw undermines the following argument: 'Students at elite universities earn higher salaries, so attending an elite university causes higher earnings'?
Answer: It ignores that high-earning students may self-select into elite universities.
If high-achieving, well-connected students disproportionately attend elite schools, the school may not be the cause of earnings — pre-existing traits may be.
In LSAT logical reasoning, a 'necessary assumption' differs from a 'sufficient assumption' in that a necessary assumption:
Answer: Must be true for the argument to work, but does not alone prove the conclusion.
A necessary assumption is one the argument cannot do without — if it's false, the argument fails — but it alone doesn't prove the conclusion.
An argument states: 'Crime rates dropped after the city installed more streetlights. Therefore, more streetlights reduce crime.' Which additional fact, if true, most seriously undermines this conclusion?
Answer: The city also deployed 200 additional police officers at the same time as the streetlights.
If additional police were deployed simultaneously, they — not the streetlights — may have caused the crime reduction, making the causal link to streetlights unreliable.