I have two cats, and they mystify me.

“What do you think your cats are thinking?” a friend of mine once asked.

I shrugged. “I have no idea what goes on in their little minds,” I said.

They are an eternal mystery to me, these cats, a furry alien presence I invited into my home on a whim and am now responsible for feeding and petting and making sure they don’t do anything foolish, like jump out a window.

They are both black, although one has white patches, and because they were rescued from an alley in Birmingham, Ala., I like to say that they’re Southern cats. “Hello, little cats,” I often greet them, although one of them, at 16 pounds, is far from little. But no matter what I say to them, the response is always the same: an intense, wide-eyed stare.

I’m never really sure what my cats want from me, but I’ve had them for over a decade, and we’ve settled into a routine. If there’s one thing I’ve learned about cats, it’s that they are creatures of habit. They sleep, they eat, they nudge me and meow when they want me to pet them. There’s a sameness to them that’s nice. No matter what’s going on, there they are, my cats, doing whatever it is they do.

Which is why I was a little surprised the other day when I returned home and noticed something different about my cat Clem. “Hey, what’s that?” I said to him. He ran away. I followed him into the other room and grabbed him. There was an odd hairless patch on his flank, flecked with blood. I looked closer. Clem had had a benign cyst, and now it appeared to be draining. “Hmmm,” I said. Clem stared at me. I foresaw an expensive bill.

A couple of days later, I stuffed Clem into his box and brought him to the vet. He wept when I carried him down the street, and in the car and at the vet’s office. Hoping to placate him, I opened the door to his box and let him poke his head out. He wept some more. It occurred to me that this was Clem’s first major health problem. Someday, I thought, this cat will die.

I did a quick mental calculation. Clem is 10. How many years does he have left? Sure, cats can live into their 20s, like that creepy mean cat my parents used to own. But it seemed safe to assume that Clem has entered the latter half of his life, and this thought made me unreasonably sad. And so even though I enjoy making fun of people who take extreme measures to keep their pets alive — I often tell my sister that her ancient diabetic cat, who requires daily insulin shots and is one of the most consistently unpleasant animals I’ve ever encountered, should be put to sleep — I sent Clem off to surgery without thinking twice, or even asking for a price estimate. Later, when I called the vet to check on him (“Clem Foss? He’s doing fine.”), I felt completely ridiculous.

I’ll be honest: I’ve never believed that the life of a cat is as valuable as the life of a human. And yet there I was, contemplating Clem’s mortality, and becoming quite depressed about it. What is it about pets? I wondered. Why do we care about them so much? I was reminded of my friend Marnie’s observation that people take better care of their pets than they do of themselves.

I got a glimpse of the lengths to which people are willing to go to demonstrate their love for their pets when I wrote an article about the Alabama Pet Cemetery, a half-acre graveyard on a small hill outside Birmingham, Ala. I drove out there with Roxanne Cunningham, one of the cemetery’s owners and a licensed veterinary technician, and wandered the grounds, stopping to look at headstones inscribed with names such as P.J., Lady and Max. Many of the animals, Cunningham said, were buried with trinkets: favorite blankets, balls, poems, even rosary beads. Some people even hold funerals for their pets, which range from simple to stately.

I interviewed Pat Blosser, founder of the International Association of Pet Cemeteries and asked her what inspired people to invest in a burial plot for their pet. She spoke of the strength of the pet-human bond, and an animals’ vast capacity for love. “There’s not a human being in the world that can give unconditional love,” she said. “There is nothing as faithful and devoted as a dog.”

Personally, I don’t know whether cats are capable of love. But I do know that since his surgery Clem has been even more affectionate than usual, when he’s not trying to shake the plastic cone, which is supposed to prevent him from chewing his sutures, off his head.

When I returned home after a particularly trying day, worried about a friend who had been hospitalized and a relative who had lost his job, Clem collapsed on the couch behind me, placed his head on my shoulder and started purring.

Unconditional love?

I have no idea.

But it went a long way toward explaining why we do the things we do for our pets.

Foss Forward makes a weekly appearance in print, in The Gazette’s Saturday Lifestyles section.