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A Priori (Legal Definition And Meaning: All You Need To Know)

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A Priori Meaning

A priori is a Latin phrase meaning “from the earlier” used in different disciplines like law and philosophy to present different types of arguments, knowledge, or justification based on evidence or experience.

The phrase “a priori” is used to present arguments based on reason or knowledge you already have.

It’s like a “cause and effect” argument.

If one fact is true, we can then deduce fact two.

For example, a grandmother is a woman having a child who in turn had a child.

This is a type of argument that can be made a priori as it’s based on a fact that is known in advance or knowable.

On the other hand, a woman with three children is a posteriori argument as you can only know that the woman has three children after the fact is given to you.

A Priori Definition

What is the definition of a priori in the English dictionary?

According to the Merriam-Webster dictionary, a priori is defined as follows:

Relating to or derived by reasoning from self-evident propositions

Another good definition offered is:

Formed or conceived beforehand

According to Dictionary.com, the definition of a priori is:

From a general law to a particular instance; valid independently of observation

A Priori Legal Definition

In law, an a priori is a type of legal argument that is made where a set of facts or ideas are considered as a given.

For example, a priori, a contract is not valid if the signing party did not have legal capacity.

Alternatively, a priori, a crime requires the commission of the act (actus reus) and the criminal intent (mens rea).

According to the Legal Information Institute, the legal definition of a priori is as follows:

A Latin term meaning “from what comes before.”  In legal arguments, a priori generally means that a particular idea is taken as a given.

A Priori Knowledge

When referring to an “a priori knowledge”, we are referring to knowledge that is acquired or had and unrelated to any of our experience.

An a priori knowledge is the knowledge that comes from before.

Immanuel Kant, in his Critique of Pure Reason (1781; 1787), explained that mathematical knowledge was considered a fundamental a priori knowledge.

With mathematical knowledge, there are many things that can be explained a priori.

For example, if we say that blue is a color, that’s an a priori knowledge as it’s a known fact.

However, if we say the house is painted in blue, that’s an a posteriori knowledge that we need to observe the house to then claim that it’s blue.

A Priori Examples

Let’s look at a few examples of how the phrase a priori is used so you can better understand its meaning:

  • If the defendant was detained by the police, a priori he could not be the suspect for the crime committed at the same time
  • Without any changes to the company’s expenses, a priori, it will not be possible to save more money
  • Two liters of liquid added to two liters of another liquid makes a total of four liters of liquid

A Priori vs A Posteriori

What is the difference between a priori and a posteriori?

In Latin, a priori means “from what is before” and a posteriori means “from what is after”.

An a priori argument is a type of argument that you can make based on the knowledge that you already have.

For example, if one year is 365 days, then 2 years is 730 days.

This is a type of argument that is said to be from causes to effect.

On the other hand, an a posteriori argument is one that you can only make after a fact is known.

For example, the law was in effect for 40 years from 1945 to 1985.

With this factual statement, you will only know that the law was in effect for 40 years after 1985.

As a result, through reasoning alone, you will not be able to make an a posteriori argument.

An a posteriori argument is said to be from effect to causes.

A Priori Takeaways 

How do you define a priori?

What is a priori in simple terms?

In essence, a priori is a term used to refer to facts that are considered as true without having to observe anything or acquire any experience to discover the fact.

Very often, a priori involves deductive reasoning where a general concept is applied to a specific case or specific conclusions are drawn from a general fact.

The term a priori comes from Latin and is literally translated to mean “from the latter” or “from the earlier”.

A priori is often contrasted with the phrase a posteriori which is a fact that is derived from observation or experience.

Typically, a posteriori is used in the context of inductive reasoning.

Let’s look at a summary of our findings.

A Priori Means

  • A priori means “from the earlier” in Latin
  • A priori is a fact, argument, justification, or conclusion that is derived from self-evident reasoning without having to rely on observation or experience
  • For example, the sky is blue is an a priori knowledge 
  • Typically, a priori arguments use a general principle or law and make specific deductions 
  • In contrast, a posteriori is a type of fact, argument, or justification that can be made after a fact is observed or experience acquired (it is generally used in inductive reasoning)
A fortiori 
A priori probability
Ab initio
Abductive reasoning
Deductive reasoning 
Ex ante 
Ex parte 
Inductive reasoning 
Off the verandah 
Preconceived idea 
Relativized a priori
Who is Immanuel Kant
A contrario
A fighting chance
A foregone conclusion
A free ride
A good deal 
A grain of allowance 
A maiore ad minus
A minore ad maius 
Ab initio 
Reductio ad absurdum 
What is an argument
What is argumentation theory 
What is rhetoric

Editorial Staffhttps://lawyer.zone
Hello Nation! I'm a lawyer and passionate about law. I've practiced law in a boutique law firm, worked in a multi-national organization and as in-house counsel. I've been around the block! On this blog, I provide you with golden nuggets of information about lawyers, attorneys, the law and legal theories. Enjoy!


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