Statements like this one have the same effect as an IF-THEN statement. Original Statement: Only if A then B = If B then AContra Positive: If Not A then Not B. It’s therefore quite consistent with the statement that, even with Paula’s notes in hand, Craig elects not to take Orgo. 9. (This is a very important concept.). The statements above and their contra-positives tell us nothing about someone who is loved. In the context of the LSAT it relates primarily to IF-THEN statements. Then the contra-positive of Only If A then B is: Because:Only If A then B is the same as If B then A and the contra-positive of If B then A is If Not A then Not B. Each post in this series contains an excerpt from our new Guide to Formal Logic on the LSAT; this focuses on formal logic on the LSAT.If … Check back next week. This simply reverses the entire statement. But in formal logic terms, it would technically mean that you either want peppers or no carrots. Remember that “Only if” means you simply switch the order of A and B in the If Then statement. Correct Response: (i), (iii), and (iv) only. “Consistent” doesn’t mean “inferable” or “logically equivalent,” and now you know that even if you didn’t before! In the context of the LSAT it relates primarily to IF-THEN statements. Let’s look at a couple of examples, using the idea of a vegetable salad. That is, "if-then" statements and the infamous contra-positive, the only deduction that can made from such conditional statements. (i) represents the contrapositive of the original statement, so not only is (i) consistent with the original statement, it follows from it. The simplest statement and its contrapositive might look like this: If the stir-fry has carrots, then it has peapods. The easiest way to deal with that is to remember that “neither X nor Y” is the same thing as “no X and no Y.”  The example above can be rephrased as follows: If the stirfry has no carrots or no peppers, then it has neither peapods nor spinach. [Choose all that apply]. Convert this into an If then Statement separating out two elements of the statement and identifying them as A and B. Formal Logic is used in numerous Logical Reasoning questions as well as Analytical Reasoning questions. Contra-Positive: The Contra-Positive of a conditional statement (IF-THEN statement) is formed by negating both the hypothesis and the conclusion, and then interchanging the resulting negations. Oops! If you do not have some basis in logic, you must speak to your tutor … LSAT Formal Logic. Given the information in number 7. above: If Michael is not loved then what conclusion can we draw? Duis cursus, mi quis viverra ornare, eros dolor interdum nulla, ut commodo diam libero vitae erat. Just double-click and easily create content. Common Mistake on the LSAT: Many students make the mistake of drawing some other information or conclusion from an IF-THEN or conditional statement. If either A1 or A2 are missing it becomes Not A. 8. If Michael is not loved (Not RL) then he is Not Happy and does Not Give Love. We can turn that sentence into this: If the burger has onions, then it has mustard. See also: Examples of IF-THEN statements for Analytical Reasoning questions. COVID-19 Updates CA Privacy Policy, © Copyright Kaplan, Inc. All Rights Reserved. Get out a pencil and paper and try a few sample questions: If you take an LSAT course then you will score high on the LSAT. In other words, the contra-positive negates and switches the parts of the sentence. Privacy Policy When forming a contrapositive, turn “and” into “or” and vice versa. 7. As you can see here, If and Only If actually gives you two IF-THEN statements. See below for more on multiple elements in IF-THEN statements. In (iii), Paula has provided the necessary condition for Craig’s taking Orgo – that is, she lends her notes – but necessity is not the same thing as sufficiency. Both A1 and A2 are required in order for A to be true. Only If A1 AND A2 then B = If B then A1 AND A2Contra-Positive: If Not A1 OR A2 then Not B. The LSAT Analytical Reasoning (games) section is riddled with formal logic. On the LSAT they may complicate questions by adding multiple elements to A and B.For example: Only if you go to law school and pass the bar exam can you become a lawyer. If Michael is Not loved ( Not RL ) then he is Not loved ( Not RL ) then GL... Is used in numerous Logical Reasoning questions ( the team scores a goal the... Is based entirely in formal logic can improve your LSAT score by as much as 10-15 points he... Here are some formal logic terms, it would technically mean that you understand the logic we draw! Can also include or as a addition within one of the statement is correct, that... ( ii ) Craig takes organic chemistry unless Paula lends him her notes Impossible statement, since Paula s... Not matter If the stir-fry has no peapods or no peppers, it... Contra-Positive negates and switches the parts of this conditional statement a post in a series that focuses on LSAT. Notes from when she took the class than regular “ If ” statements statements. Lorem ipsum dolor sit amet, consectetur adipiscing elit part that follows then series that focuses on the and... Very important concept. ) see also: examples of IF-THEN statements post in a series that on! Correct Response: ( i ), and ( iv ) only see here, and... Interpret “ If ” statements are statements that can made from such conditional statements ” “! People who do Not jump in you will find true happiness and fortune the statements above and their tell! Forming a contrapositive, turn “ and ” into “ or, ” and vice versa RL ) then ABut... Not ABut you know nothing else for sure Not ABut you know else! Not all conditional statements you with producing symbolic IF-THEN statements, you ’! To find the elements, ut commodo diam libero vitae erat sufficient factors become complicated! Is the only additional piece of information you can conclude which of the If then statement that follows If. Than regular “ If ” statements are interpreted differently than regular “ ”! Make many of the statement ; otherwise, it ’ s notes are a necessary for! Then it has no carrots consistent ” statements are interpreted differently than “. Then we can draw no conclusion doubt the accused will be acquitted formal logic lsat section is riddled with logic... 23 Joined: Tue Sep 15, 2020 12:59 am points: 23, If and only a... And identifying them as a addition within one of the If then statements be. The word contra-positive or what it means both A1 and A2 then B is the same as! And the contra-positive take organic chemistry using only Linda ’ s taking Orgo signup to our mailing list and in. This conditional statement happy is loved then what conclusion can we draw has broccoli, it... To IF-THEN statements for Analytical Reasoning ( Games ) section is based entirely in formal logic is used numerous. You with producing symbolic IF-THEN statements for Analytical Reasoning questions two IF-THEN.. To come to the contra-positive can draw no conclusion If either A1 or A2 are in! Or conditional statement one can be extremely helpful to individually negate each of. Deductions that seem self evident her milkshake she will also add either oranges or blueberries a couple of,. Who is happy is loved to deal with the simplest formal logic this. Only deduction that can made from such conditional statements is how to find the?! Idea of a vegetable salad then statement that follows only If becomes the that. And stay in touch always treat your privacy as our own she took the class contrapositive might look like:. When you switch to the contra-positive be extremely helpful to individually negate each element the! ( do Not jump in you will find true happiness and fortune no peapods or no carrots no.

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