00:01
Okay, here i want to see if this argument is valid.
00:03
What we have is p implies q.
00:07
So if p then q followed by not q does that mean therefore p must be true? so first thing we do is write this as a statement.
00:19
So what i have then is p implies q and not q implies p.
00:32
If that is true, and the argument is true.
00:36
Now, here then drew a truth table.
00:41
If you have p and q, there are four possible situations.
00:45
T, t, f, f, f, and f, f, always that order.
00:54
And the first column we do is p implies q.
00:58
Now with p implies q, you have to know it's always true unless you have tf.
01:05
So t t t t, t is true.
01:06
True, tf is false, ft is always true, ff always true.
01:15
Then we do not q.
01:18
So let's draw a line down here and we'll do here, not q.
01:29
Well q is tf, tf, here is q here, tf, tf, reverse that and we get ft, ft.
01:40
So not q, reverse a q...