Alex Marcus: GMAT & LSAT Trainer - 16+ years of experience

Recent Posts

How LSAT formal logic applies directly to the law


powered by

My Blog

How LSAT formal logic applies directly to the law

Please note that this article discusses formal logic concepts, such as "conditional statements" and "the contra-positive". A full explanation for these concepts won't be provided here, but that shouldn't be necessary. For anyone not familiar with these concepts, just know that this article isn't expressing an opinion about the Bill of Rights (see below), but a formulaic application of formal logic.

The LSAT Analytical Reasoning (games) section is riddled with formal logic. That is, "if-then" statements and the infamous contra-positive, the only deduction that can made from such conditional statements. We all know that the law is all about logic, which is the foundation of the LSAT, but isn't most of life all about logic? What is it about the law that requires students to agonize over switching and negating, changing "or" to "and", while remembering that "neither...nor" means "not...and"?  A great answer can be found in the good old Bill of Rights.

Let's start with the Fourth Amendment and how formal logic shows that  warrantless searches are actually constitutional (BTW - I'm a libertarian):

"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."

This sentence can be accurately (though not completely) rephrased into four conditional statements:
IF unreasonable search THEN search not permitted.
IF search permitted THEN search is reasonable (contra-positive of previous statement)
IF warrant THEN probable cause AND particular description.
IF no probable cause OR no particular description, THEN no warrant (contra-positive of previous).

Notice how the second conditional statement provides the only necessary condition to conduct a search: it needs to be reasonable. Nothing about warrants.

Yes, yes, this begs the question of what is meant by "reasonable", but that's beyond the scope of this article (but not my LSAT training, BTW).

For those familiar with LSAT formal logic - did you notice the "not...unless" phrase in "no Warrants...but upon"? And that's not the only place you'll see it in the Bill of Rights, but I'll get back to that.

Back to the Fourth Amendment. Nowhere does it say, or even imply, the following:
IF search permitted THEN warrant.
Or the contra-positive:
IF no warrant THEN no search permitted.

To repeat: the two above conditional statements are NOT logical deductions that can be drawn from the Fourth Amendment. The logical implications of a warrant support this:
IF warrant THEN search permitted.
Or the contra-positive
IF search not permitted THEN no warrant.

This creates an interesting connection to the explicit text, namely:
IF warrant THEN search is reasonable.
(IF warrant THEN search; IF search THEN reasonable; therefore: IF warrant THEN search is reasonable).
Or the contrapositive:
IF search is not reasonable, THEN no warrant.

Fun, right? Head spinning yet? If not, then congratulations - you're ready for the LSAT. If so, then rest assured that many students are in the same boat. Just know that formal logic isn't just some abstract concept designed to drive students crazy. In fact, it has actual life or death implications, as found in parts of the Fifth Amendment:

"No person deprived of life, liberty, or property, without due process of law..."

Accurately rephrased into a conditional statement:
IF deprivation of life THEN due process.
Or the contra-positive:
IF no due process THEN no deprivation of life.

Notice the "not...unless" statement ("no...without")? 

16 Comments to How LSAT formal logic applies directly to the law:

Comments RSS
Tyrell Hooker on Thursday, October 15, 2015 9:19 AM
guest think within impressive and?
Reply to comment on Friday, October 12, 2018 6:22 AM
People also should know their rights because most people do not know that if there are no warrants, police can not do anything or search for anything in your place. People need to be aware of the things they have the a right. Thank you for posting this article and letting many people know about what are their rights. Some authorities just used their power to abuse people and people should be ready for those authorities.

Nettikasino bonukset 24 on Monday, October 19, 2015 7:11 AM
amateurs have no a good clue?
Reply to comment

Marta Corron on Tuesday, October 27, 2015 1:17 PM
wall in the hallway?
Reply to comment

Roy Bordeau on Tuesday, October 27, 2015 4:02 PM
The contemplation and even idea?
Reply to comment

car accidents on Tuesday, November 10, 2015 7:46 AM
The LSAT Analytical Reasoning (amusements) segment is loaded with formal rationale. That is, "if-then" proclamations and the scandalous contra-positive, the main derivation that can produced using such restrictive articulations. We all realize that the law is about rationale, which is the establishment of the LSAT, yet isn't the vast majority of life about rationale? What is it about the law that obliges understudies to struggle with exchanging and discrediting, evolving "or" to "and", while recollecting that "neither...nor" signifies "not...and"? An incredible answer can be found in the great old Bill of Rights. Thanks!
Reply to comment

asdfas on Thursday, December 22, 2016 2:14 AM
Reply to comment on Thursday, December 22, 2016 2:15 AM
The two above restrictive proclamations are not coherent conclusions that can be drawn from the fourth amendment. The consistent ramifications of a warrant bolster this.
Reply to comment

researchpaperwriter on Monday, December 26, 2016 7:00 AM
This blog shared articles may helpful to find formal logic applies directly to the law of this blog. The details are everything I have read from this website, and thanks for every update.
Reply to comment

Personal injury lawyers on Tuesday, May 09, 2017 3:28 AM
I am happy to find so many useful information here in the blog post, we need develop more strategies in this regard, thanks for sharing.
Reply to comment

Tax Lawyer Toronto on Friday, June 09, 2017 5:02 AM
Fantastic logical article. Thanks for the info.
Reply to comment

Toronto Tax Lawyer on Friday, June 09, 2017 5:37 AM
I went thorough the blog and thought its just awesome. Thanks for logical explanation.
Reply to comment

personal-injury-solicitors on Sunday, November 26, 2017 6:47 AM
Thanks for this I will try more
Reply to comment

Franklin on Monday, June 04, 2018 7:32 AM
Wow! what a nice post.
Reply to comment

premieressay on Saturday, June 23, 2018 12:44 PM
This article with explain to the reader the comparison between civil and common law. There are many differences among the two but there are also several similarities. It also talks about the establishment of both laws such as where they came from, how they were brought up, and where they are in today’s societies.
Reply to comment

djhd on Tuesday, June 26, 2018 3:51 AM
Hello! I think you will write my paper reviews need help in writing essays. Click and get more information
Reply to comment

Add a Comment

Your Name:
Email Address: (Required)
Make your text bigger, bold, italic and more with HTML tags. We'll show you how.
Post Comment
Website Builder provided by  Vistaprint