# The author uses the word "immediacy" (line 39) most likely in order to express

nicolebet on February 21, 2020

Contrapostives

(Sorry if this has posted twice, LSATMAX kept crashing) I understand that we negate and reverse. However, the lecture states, "Lastly, if you are not in medical school, we can say you are not a doctor" (12:40-12:45 timestamp) This reversed is: if you are a doctor, then we can conclude you went to med school. When taking formal logic the (if, then) is very important in regards to antecedents and consequents.... Is this the same way the lesson is structured? It does not seem correct to state you are not currently IN medical school, therefore you are not a medical doctor. Maybe I was thrown off by the language used when you reversed the statement, making it currently in Med school, vs an inference that could have been made. Also, Validity is important however, what about soundness and cogency when approaching the LSAT, are they important? Is it better to not think of the formal/ symbolic logic I learned in my undergrad philosophy courses, and approach the LSAT's logical reasoning/ sufficient & necessary using LSATMAX's tips?

Replies

nicolebet on February 21, 2020

Is this basically referring to modus ponens and modus tollens in formal logic?

shunhe on February 21, 2020

Hi @nicolebet,

Thanks for the question! I think what the instructor meant to say was that the original statement

Doctor â€”> Medical School

Means that if you are a doctor, you went to medical school.

And so the contrapositive

~Medical School â€”> ~Doctor

Should mean that if you didnâ€™t go to medical school (which I think the instructor meant by â€œif you arenâ€™t in medical schoolâ€), then you arenâ€™t a doctor. I would definitely say to feel free to use what youâ€™ve learned in your formal/symbolic logic philosophy classes, though really the only logic that will really be tested on the LSAT is first-order logic. The types of questions being asked really arenâ€™t that complicated if youâ€™re a studier of logic (e.g. definitely no modal logic, and you donâ€™t even really need to know predicate logic). Really the most complicated it gets isnâ€™t significantly harder than having to apply De Morganâ€™s from time to time.

As for sound arguments, we always assume that the premises in the stimulus are true. Thus, if an argument on the LSAT presented is valid, we assume it is sound as well, though you wonâ€™t ever be asked about soundness. Same goes for cogency, you wonâ€™t be asked about it, but cogency I suppose is related to the idea of picking the â€œbestâ€ answer.

The part of the video you pointed out is just an application of modus tollens. Elsewhere, yes, you will use modus ponens, though you donâ€™t have to actually know these terms. The LSATMAX terms are ways of making first-order logic accessible for people who arenâ€™t familiar with logic.

Hope this helps! Feel free to ask any other questions that you might have.

nicolebet on February 23, 2020

Thank you so much!