A Concise Introduction to Logic, Patrick J. Hurley, Wadsworth, 2006, 9th ed,. 8.7, III, 3 p. 448

The artist who painted the Mona Lisa was a Florentine. Leonardo is the artist who painted the Mona Lisa. Therefore, Leonardo was a Florentine. (Ax: x is an artist; Pxy: x painted y; Fx: x was a Florentine; m: the Mona Lisa; l: Leonardo)

1.     (∃x)[Ax • Pxm • (y)[(Ay • Pym) ⊃ y= x] • Fx] 2.     Al • Plm ∴ Fl 3.     Ar • Prm • (y)[(Ay • Pym) ⊃ y= r] • Fr 4.     (y)[(Ay • Pym) ⊃ y= r] • Ar • Prm • Fr 5.     (y)[(Ay • Pym) ⊃ y= r] 6.     (Al • Plm) ⊃ l= r 7.     l = r 8.     Fr • Ar • Prm • (y)[(Ay • Pym) ⊃ y= r] 9.     Fr 10. Fl

1 EI 3 Com 4 Simp 5 UI 2,6 MP 3 Com 8 Simp 7,9 Id