I remember reading one of Philip Jose Farmer's stories in one of the SF magazines when I was a teenager in the 70s. There was some kind of alien spaceship - the details weren't important - that appeared over the Earth and slowly, inexorably began erasing people's memories.
The story was set in the near future (i.e., now) when electronic calendars were commonplace, and at first everybody thought there was a bug in the software that was making the calendars skip dates. Then they gradually realized that their own memories were vanishing - beginning with the most recent events, and gradually working backward. Finally the characters realize that the situation is hopeless and there is nothing they can do against this progressive amnesia.
The story ended with the words, "Perhaps there are two kinds of memory."
I thought about this story a lot when I was losing my father to Alzheimer's.
There are, indeed, two kinds of memory: there are the memories of facts, names, places, and events, which allow us to navigate in this confusing world. And then there are the deeper memories - feelings and dreams, which are of no practical value to the analytical mind but which make us who we are and give our lives substance. One of these is perishable, the other durable.
Because my own memory is imperfect, I can't recall the title of the story, the date, or the magazine in which it appeared. I only remember the impression it made on me - perhaps at that deeper level of memory. But I am quite sure it was one of Philip Jose Farmer's works.
Any PJF fans out there who can help?