What is a valid argument?

What is a valid argument?

1. Valid deduction and true conclusion

Premis 1: Humans are mammals,

Premis 2: mammals are animals

Conclusion: therefore humans are animals

2. Valid deduction and false conclusion

Premis 1: Humans are trees,

Premis 2: trees are plants

Conclusion: therefore humans are plants

3. Invalid deduction and true conclusion

Premis 1: Humans are mammals,

Premis 2: Cats are animals,

Conclusion: therefore humans are animals

4. Invalid deduction and false conclusion

Premis 1: Humans are animals,

Premis 2: Roses are plants,

Conclusion: therefore humans are plants

Only the first case is a valid argument. Besides you can have 2 persons both believing that “humans are animals” but one believes it based on case1-like type of reasoning while the other one believes it based on case3-like type of reasoning. So, when testing your knowledge, verify not only whether your opinion is true or false, but also if your reasoning is valid! And if your opinion is false, don’t look just for the truth in your premises but also the soundness of your reasoning!