What is a Valid Argument?

Validity is an important concept in logic. This video introduces the concept of a "valid" argument.

[chelsiebrooks]

I love your video. I'm taking a philosophy course and I was so confused on what the meaning of valid and invalid deductive reasoning meant, until I seen this video. You explained it a whole lot better.
Thank you.

[jjaya]

I like to think of the premises & conclusions in syllogisms in terms of Venn diagrams.
Example 1:
Premise 1: "All actors are robots" (draw circle labeled 'actors', and shade 100% of it to indicate all it as robot-filled)
Premise 2:"Tom Cruise is an actor" (given we're told Tom Cruise is an actor, find his place in circle)
Conclusion: "Tom Cruise is a robot" (upon looking at the 'actor' circle, which is 100% robot shaded, it's logical to conclude Tom's secret identity)

Example 2:
Premise 1: "All actors are robots" (draw circle labeled 'robots', and inside shade a small area for 'actors')
Premise 2:"Tom Cruise is a robot" (given we're told Tom Cruise is a robot, find his place in circle)
Conclusion: "Tom Cruise is an actor" (upon looking at the 'robot' circle, which only has a part shaded for actors, it would NOT be logical to definitively conclude Tom is an actor, when there exist possibility he could be something else)

[DoubleDee]

I have test over this tomorrow and it fucks with my head so much

[isaiahwilson]

Great Video my friend it really help me comprehend the difference between a valid and invalid argument!!!!

[David-xyzu]

This is explained SO much better than in my textbook or by my professor.  Thanks a lot!

[pandotpira]

in categorical syllogism simply look for the three categories in their proper place.

(category 1) (category 2)
(category 3) (category 1)
(category 3) (category 2)

example

(c1 robots) are (c2 actors)
(c3 tom cruise) is a (c1 robot)
(c3 tom cruise) is an (c2 actor)

c1 = robot
c2 = actor
c3 = tom cruise

example

all gods are mortals
men are gods
men are mortals

or

all men are gods
mortals are men
mortals are gods

or

mortals are men
gods are mortals
gods are men

all these are valid arguments as long as the categories are in their right places.

[marialaureano]

The best video I could find!! Thank you!

[haeatawatson]

OK, I don't get this. You say at 1:47 that "IF all the premises are true, then the conclusion CANNOT be false." Then you say, "IF all the premises are true, then the conclusion CAN be false." Which one is it?

[logangomez]

I'm having trouble with the symbols and propositional argument forms.

[chartphred]

Ok, here's what I DON"T get!  If the first example says that All actors are robots and Tom Cruise is an Actor therefore he's a robot, we know is actually not true, yet we assume it is in the context of this argument... so why can we not assume similar things in the second argument where it might be that 'All Actors a robots'... I mean we know that its not true in both cases yet the example in the second one says invalid... that makes no sense to me.

[haileluel]

some premises are valid ? true or false?

[mollie]

Great tutorial. (Tom Cruise is a RONbot though ;) )

[pandotpira]

Kevin deLaplante is a logic teacher
Batman is Kevin deLaplante
Batman is a logic teacher

this is also valid

[wetsaw]

So is evolution theory an invalid argument?

[pandotpira]

rose is not blue
violet is not rose
violet is blue

[haileluel]

HI Kevin your vedio is important so pless answer me for some my questions

[mrdave]

What you do not understand is if a equals b and b equals c, a does not equal c. Valid arguments are not valid. Truth is not always what people have been taught and some believe all valid arguments are valid simply because they were taught that.