His name is Tom. He is 63, tall and lean, a contracts lawyer in a small Oregon town. A few wisps of hair still reach across his scalp. The moustache I have never seen him without has faded from deep brown to silver. The puns he tormented my younger brother and me with throughout our childhood have evolved, improbably, into the funniest jokes my 6-year-old son has ever heard. I love my dad fiercely, even though he's beaten me in every argument we've ever had except two, and even though he is, statistically and generationally speaking, a parasite.