--- title: "What makes an argument valid" description: "An argument can be valid and still have a false conclusion, and it can reach a true conclusion by luck. This topic teaches two separate checks for deductive arguments: whether the conclusion follows f" canonical: https://lightmysky.com/learn/personal-and-social-development/what-makes-an-argument-valid-mt_W72nTJmeOI source: https://lightmysky.com/learn/personal-and-social-development/what-makes-an-argument-valid-mt_W72nTJmeOI.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # What makes an argument valid An argument can be valid and still have a false conclusion, and it can reach a true conclusion by luck. This topic teaches two separate checks for deductive arguments: whether the conclusion follows from the premises and whether the premises are true. Subject: Personal & Social Development · Area: Ethics & Philosophy · Ages 16 to 18 Page: https://lightmysky.com/learn/personal-and-social-development/what-makes-an-argument-valid-mt_W72nTJmeOI ## Ready when they can - Set out an argument as premises and a conclusion, in your own words - Give an example of a valid argument with a false conclusion and explain why it is still valid - Say what has to be added to validity to get soundness ## Lesson: Valid does not mean true An argument offers premises, or reasons, for a conclusion: the claim the speaker wants you to accept. Kant's objection becomes: framing an innocent person violates a moral limit; we must not violate that limit; so we must not frame them. Separate the claim from its reasons. Therefore and so often signal conclusions; because and since often signal premises. Read the meaning too: these are clues. Arguments can omit them and have different numbers of premises. A deductive argument is valid if its premises cannot all be true while its conclusion is false. Validity does not establish that the premises are true. Consider: all bicycles are plants; this is a bicycle; therefore this is a plant. If both premises were true, the conclusion would follow. Its false first premise makes it unsound. In general, a false premise can occur with either a true or a false conclusion. *(drawing: The conclusion follows under the assumptions. That does not make those assumptions true.)* **Example.** True claims do not automatically form a valid argument. Consider: the club meets today; its badges are blue; therefore its room has a window. Suppose all three claims happen to be true. The premises still do not force the conclusion: the club could meet today with blue badges in a room without a window. That possible case has true premises and a false conclusion. A sound argument is valid and has all true premises. Check both conditions separately. First ask whether the premises force the conclusion. Then check every premise against the facts. For example: all dogs are mammals; this animal is a dog; therefore this animal is a mammal. The form is valid. If the animal really is a dog, both premises are true and the argument is sound. **Example.** To show invalidity, find a possible case with true premises and a false conclusion. Consider: if the door is locked, the hall is quiet; the hall is quiet; therefore the door is locked. The door could be unlocked while everyone is outside. Both premises could hold while the conclusion fails. This is affirming the consequent: taking the stated result as proof of its condition. **Recap.** Validity checks the link from reasons to claim, and adding true starting points turns a valid argument into a sound one. *Original teaching, exercises and flashcards written for this dataset. OpenStax's Introduction to Philosophy was consulted for facts and topic structure.* ## Practice 8 questions on this page, each with its working shown. ## Optional connections - [Structuring an Argument](https://lightmysky.com/learn/english/structuring-an-argument-mt_HYPdD7Zqxu) ## Opens up - [Facts, Values and the Gap Between Them](https://lightmysky.com/learn/personal-and-social-development/facts-values-and-the-gap-between-them-mt_cvgg2UNDzv)