predicate truth trees 3 mp4

Here's the last rule that we need to deal with predicate truth trees and it's a rule for when the main operator is a negation of a quantified statement, so this is a negation of a universal or a negation of an existential statement. Here's what we do: we push that tilde through and it only hops one place it goes right to the other side of the quantifier it doesn't go further in, it doesn't attach to anything in here it just hops one place. And as it does that, as it hops here or as it pushes through, it always changes the quantifier. If it's "X" it will become "EX," if it's "EX," it will become "X." So let's do that now. Change the quantifier, tilde goes right on the other side of the quantifier. Everything else exactly the same as it was. And with "EX," the quantifier becomes "X," the tilde moves in one place, everything else stays exactly the same. And now you are ready to use, in this case here, the rule for "EX," take off the quantifier replace with a brand new constant. Same thing with this universal. Take off that replace the "x's" with every constant that shows up. And that's it! And always remember to check those off.