My father, Philip Weingarten, is 90. He wears hearing aids in both ears. At night, before he goes to bed, he removes them as he stands with his head above an open dresser drawer. That is because, if he dropped one on the floor, he could never find it. He cannot see the floor.

His right eye sees nothing. The sight that remains in his left eye is so limited that, to read, he must use a machine that magnifies each letter to the size of a baseball. In this manner, he reads The Washington Post every day, all day. The retina in his functioning eye is a rubble of scar tissue, so ravaged from diabetic damage and macular degeneration that his doctor doesn't know how he sees anything at all. Somehow his brain has learned to cobble together into vaguely recognizable images the fractured signals from the few neurons that still fire.

When he walks the halls of the assisted-living facility in which he lives, people greet him by name, but he cannot do the same in return. The friendly blobs are indistinguishable. I have always joked that my father is the reincarnation of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne. That is because he was born on June 28, 1914, the day the archduke and his pregnant wife were assassinated, touching off World War I. Ferdinand's dying words were selfless -- concern for his wife and family -- which pretty much sums up the way my father has lived his life.

Though his eyes have betrayed him, his mind remains as sharp as yours or mine. He was an accountant, and has attended to his own affairs ably until just last week, when he found he could no longer see well enough to write checks or keep records. And so my wife and I brought him to the bank, where he conferred power of attorney on his daughter-in-law. Intending no disrespect, the banker began by directing questions to my wife and me, but quickly checked herself when my father volunteered not only his Social Security number but the precise number of his savings account.

He moves in a determined shuffle, behind an aluminum walker. When he ventures outside, he needs a companion to warn him of the presence of a curb, or a sidewalk anomaly. The ground is a soupy mist to him, swallowing his legs at the thigh. Daylight can play mischief with his eyesight. Sometimes, the empty streets before him are aswarm with pint-sized people, or blocked with poplar trees, or are a landscape of yawning craters. These are the only things he sees in sharp focus, because they bypass his ruined eyes entirely. They are inventions of his brain, a medical syndrome not uncommon in people with profound loss of vision. They are hallucinations, but not delusions. He knows they are unreal; still, it is an act of faith and no small courage to step confidently forward into an abyss, just because someone you love tells you it is safe.

It is through this foggy soup and minefield of phantasms that my father will walk this afternoon, with me at his side, into a church in suburban Maryland. There -- as he has done every four years since he chose Roosevelt over Landon -- he will cast a mathematically insignificant vote for president of the United States. Because he knows it is the right thing to do.

So, what are you doing today?

Gene Weingarten is a staff writer for the Washington Post Magazine.