Explain, using a concrete example, why we should not allow the following inference when using $\textbf{ UG. }$ What restriction then is required on the use of $\textbf{ UG? }$

Question

Explain, using a concrete example, why we should not allow the following inference when using $\textbf{     UG.    }$  What restriction then is required on the use of $\textbf{     UG?    }$

Quizplus · Accepted Answer

The Answer is It could allow us to move from a true statement to a false one. For example, if Lxy = "x loves y", then from the fact that x loves someone it does not follow that x loves everyone. UG requires that the variable that is universally quantified be one that does not occur previously in a line obtained by EI (restriction 2)

Explain, Using a Concrete Example, Why We Should Not Allow UG. \textbf{ UG. } UG.

Explain, Using a Concrete Example, Why We Should Not Allow $\textbf{ UG. }$