Proposition facts for kids

A proposition is a special kind of statement or idea. In philosophy and logic, a proposition is something that can be proven to be either true or false. It's like saying, "Is this statement a fact, or is it not?"

For a statement to be a proposition, it must be possible to check if it's true or false. If you can't decide if it's true or false, then it's not a proposition. Many people who study logic use the words statement and proposition to mean the same thing. Sometimes, propositions are shown using capital letters like P, Q, and R.

What is a Proposition?

A proposition is a sentence that makes a claim about something. This claim can then be tested. For example, "The sky is blue" is a proposition because we can look at the sky and see if it is blue. If it is, the proposition is true. If it's not (maybe it's night or cloudy), then the proposition is false.

Examples of Propositions

Here are some examples of propositions:

• "The Earth is round." (This is a true proposition.)
• "Cats can fly." (This is a false proposition.)
• "2 + 2 = 4." (This is a true proposition.)
• "All birds have teeth." (This is a false proposition.)

These are all propositions because we can clearly say if they are true or false.

When a Statement is NOT a Proposition

Some sentences are not propositions because they don't have a clear true or false value.

• "What time is it?" (This is a question, not a statement that can be true or false.)
• "Please close the door." (This is a command, not a statement.)
• "Wow!" (This is an exclamation, not a statement.)
• "I wish I could fly." (This is a wish, not a statement of fact.)

These types of sentences don't state something that can be proven true or false, so they are not propositions.

Different Ways to Say the Same Proposition

A single proposition can be said in many different ways. The important thing about a proposition is its actual meaning, not the exact words used. Propositions can look different but still mean the exact same thing. When two different statements mean the same thing, they are called synonymous.

For example:

• "Snow is white." (in English)
• "Schnee ist weiß." (in German)

These are different sentences because they are in different languages. However, they both mean the same thing: snow has a white color. No matter what language you use, the meaning is the same. So, these statements are synonymous and represent the same proposition.

Propositions in Ancient Logic

In Aristotelian logic, which comes from the ancient Greek philosopher Aristotle, a proposition is a special kind of sentence. It either confirms or denies that something happened or that a subject has a certain quality.

Aristotelian propositions often look like these:

• "All men are mortal."
• "Socrates is a man."

In these sentences, the subject (like "men" or "Socrates") has a status or quality (like "are mortal" or "is a man"). This status can be seen as either true or false.

Propositions and Meaning

Some thinkers, like those who followed logical positivism, believed that if you couldn't possibly decide if a proposition was true or false, then it was meaningless.

For example, statements about whether God or gods exist cannot be proven true or false using scientific methods. Because these statements don't have a clear way to be proven true or false, a logical positivist would say that propositions like "God exists" or "God does not exist" have no logical meaning. They aren't saying these statements are false, just that they can't be tested in a way that gives them a "truth value" in logic.

Related pages

• Axiom
• Propositional logic
• Predicate logic

See also

In Spanish: Proposición para niños