--- 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. Separating the shape of the reasoning from the truth of the parts is the first move in philosoph" 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: 2026-09-12 --- > **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. Separating the shape of the reasoning from the truth of the parts is the first move in philosophy and in every argument after it. 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 Every argument has two parts. The premises are the reasons offered, and the conclusion is the claim they support. Watch for signal words. So and therefore point to a conclusion, while since and because flag premises. Writers hide the shape, so your first job is to lay it out: premise one, premise two, therefore conclusion. Only then can you ask whether it holds up. Validity is a narrow promise. An argument is valid when the conclusion must be true if the premises are true. That is all it promises. Try this one. All cats can fly. Mittens is a cat. So Mittens can fly. If those starting claims were true, the ending would have to be true. The link holds even though the start is nonsense. **Example.** Truth and logic can split either way. Take two true claims plus a true ending they do not support. The battle of Hastings happened in 1066. Tamaracks are deciduous conifers. Therefore Paris is the capital of France. All three lines are true, yet the reasoning is empty. Now flip it. If the moon is made of cheese, then mice vacation there. The moon is made of cheese. So mice vacation on the moon. False from start to finish, but the step itself is airtight. **Tip.** Add true premises to a valid link and you earn soundness. A sound argument is valid with true starting points. Also watch the most common broken link. If it snows, schools close. Schools closed. So it snowed. Other causes close schools too, so the ending does not follow. To test any link, assume the premises are true and ask whether the conclusion could still be false. **Recap.** Validity checks the link from reasons to claim, and adding true starting points turns a valid argument into a sound one. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [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)