BY DEFINITION, THE PROPOSITION ∃X ∈ D P (X) IS TRUE WHEN P (X) IS TRUE FOR SOME X IN THE DOMAINOF DISCOURSE

76. By definition, the proposition ∃x ∈ D P (x) is true when P (x) is true for some x in the domain

of discourse. Since P (d) is true for some d ∈ D, ∃x ∈ D P (x) is true.