![true conclusion false premises true conclusion false premises](https://image3.slideserve.com/5521457/mission-impossible-is-valid-argument-with-true-premises-and-false-conclusion-l.jpg)
Which is to say that, while the conclusion is true, it’s not actually proved by the argument. And logically, the form of the argument is perfectly valid (although not sound). They might be mechanics or teachers or politicians or whatever. Both premises are false, but the conclusion is nonetheless true. It would follow if we said that ONLY actors are robots, but the first premise doesn’t say that.Īll we can assume is that in this hypothetical world, anyone in the acting profession is a robot, but robots might be doing lots of different jobs besides acting. Now, if these premises are both true, does it follow that Tom Cruise HAS to be an actor? No, it does not follow. Instead of assuming that Tom Cruise is an actor, we’re assuming that Tom Cruise is a robot. The first premise is the same, “All actors are robots”. Here’s an example of an INVALID argument: Validity is the strongest possible logical glue you can have between premises and conclusion. These are all different ways of saying the same thing. Or to put it another way, the truth of the premises guarantees the truth of the conclusion. THAT is the distinctive property of this argument that we’re pointing to when we call it “valid” - that it’s logically impossible for the premises to be true and the conclusion false. In other words, in a hypothetical world where all actors are robots, and Tom Cruise also happens to be an actor, then it’s logically impossible for Tom Cruise NOT to be a robot.
![true conclusion false premises true conclusion false premises](https://images.slideplayer.com/24/7365266/slides/slide_23.jpg)
In this case we know that in fact the first premise is false (not all actors are robots) but the argument is still valid because IF the premises were true it would be IMPOSSIBLE for the conclusion to be false. In these examples, luck rather than logic led to the true conclusion. False premises can lead to either a true or a false conclusion even in a valid argument. Validity is a guarantee of a true conclusion when the premises are true but offers no guarantee when the premises are false. IF all the premises are true, then the conclusion CANNOT be false. Nevertheless, in these examples, the conclusion is true. Here’s the standard definition of a valid argument:Īn argument is VALID if it has the following hypothetical or conditional property: To see this, try to imagine some way the world could be such that all of the premises are true. Again, to say that an argument is valid is only to say that if all of its premises are true, then its conclusion must be true. In such an instance the argument would be invalid, but the conclusion would be true. The second of these arguments has a false premise. In some circumstances, it may be that while the conclusion does not follow from the premises, the conclusion is still true.