Three days after he arrived, I entered his apartment and found in the bathroom a plastic bowl full of feces and urine and soiled baby wipes. The vanity and floor were smeared with brown. This, apparently, was part of his process of relearning how to use the bathroom. He insisted he would clean up the mess himself, forbidding me to touch it, an instruction I defied, since he tended to fall when he bent down. In the kitchen, most of a pint of two-day-old ice cream lay hardened into a sticky goo on the floor where it had fallen, out of his precarious reach. He insisted he would clean that up, too, and just hadn’t got around to it. Meanwhile, he had dropped a sheet of paper towel over the mess.

That was just day three.

My father was 80 then. He was a bright man, strong-willed and willful, and his strength of mind had served him well. Despite having been raised in poverty by a single mother, he got himself through college and Yale Law School, then built a successful law practice in Phoenix, where he lived for more than 50 years. After his marriage failed, he raised three children as a single parent. For decades, people had sought his counsel. You could not tell him what to do. He looked at me once, on one of many occasions when I was pleading with him to accept help, and said levelly, “I want you to consider the possibility that I am right and the whole rest of the world is wrong.”

In the late 1990s, after retiring from law and traveling the world, he had gotten into the habit of spending summers in Washington, where he had converted a midtown studio apartment I owned into his second home, nine miles from my house in suburban Virginia. He and Michael and I would spend weekends exploring Asian film festivals and Jewish theater and esoteric restaurants. As he got sicker, it made sense for him to move his base from Phoenix to Washington, because he could get around Washington without driving.

Before he arrived last spring, I did my best to prepare. I had set up an emergency-alert button, which he accepted as an aid to independence (but did not consistently wear). After a week or two of coming in and finding urine-soaked jeans on the floor and sometimes on him, I bought him some adult diapers, which he also accepted as an aid to independence (but did not consistently wear). I asked the condo building’s maintenance man, whom my father liked, to do housekeeping twice a week, an arrangement my father accepted because it struck him as ingenious and inexpensive. Through a friend at work, I arranged periodic visits from a social worker with the Jewish Social Service Agency, whose competence and intelligence my father respected. I thought I was ready, and for a few weeks, despite my initial shock over his condition, it seemed to work.

I should say that my description so far must make my father seem nothing but stubborn. He was stubborn, but he was also charming, resourceful, generous, kind, funny, uncomplaining, and good at making friends and allies of those around him. By enlisting friends and learning to cope, he had managed on his own longer and better, certainly, than I could have done. He had consistently proved wrong those who told him what he couldn’t do. And Parkinson’s, his doctors assured us, was a slow-moving disease. Expect only gradual change.

By last year, however, the disease was moving fast. He would eventually be rediagnosed with a particularly nasty neurological torment called multiple system atrophy, but that was later, near the end. Until the last couple of months, no one realized how sick he was, and so his resistance to impingements on his independence was understandable. Shame was another reason he wanted to be left alone. As he confessed to me more than once, he felt ashamed of his condition. One of the few times he ever cried in my presence was when he saw me on my knees, scraping hardened ice cream or jam, or whatever it was that day, off the floor. “I’m sorry,” he said. “I’m sorry. I never meant for you to scrub the floor for me.”