An argument is (deductively) valid if it is impossible for the premises to be true and the conclusion false; it is invalid otherwise.
forallx, an introduction to formal logic
In other words, a valid argument has three possible forms as below:
1. true premises, a true conclusion
2. false premises, a true conclusion
3. false premises, a false conclusion.
This thus means that an invalid argument contains true premises but a false conclusion.










