25. If x - y xy, firstly, what is the arithmetical value of xy?
"A Budget of Paradoxes, Volume II (of II)"
Augustus de Morgan
Hence we see that the Proposition "No x exist" is a Double Proposition, and is equivalent to the two Propositions "No xy exist" and "No xy' exist".
"Symbolic Logic"
Lewis Carroll
This, we know, is equivalent to the Proposition of Existence "Some xy exist".
"Symbolic Logic"
Lewis Carroll