In the building where I used to work there was a blind guy called Trevor. Trevor worked for an online estate agent on the 5th floor. What he did there I could never imagine — he had been blind since birth and had never actually seen software or property. Whatever it was, it probably involved talking. Trevor liked to talk and was surprisingly loud.

"Hello?" he’d boom when he wanted to attract your attention. “I say—” he’d begin, and then he’d wait for you to come over so he could talk to you. I spoke loudly to him too, given how loud he was, but he put an end to that. “I’m blind,” he said, “not deaf.”

Trevor had a white cane. He smoked and went out into the courtyard a couple of times every day, tapping away with his cane and booming at people.

One spring another blind man started working in the building, on the ground floor. His name was Frank. Frank had a guide dog called Bruce, a white Labrador with a strangely lopsided face and a tongue that was too big for his mouth. Bruce appeared to have the IQ of a harness. He wasn’t a very good guide dog. On their first day in the building, Bruce dragged Frank through the lobby.

“Bruce!” Frank called out. “Stop, damn you! Bruce!”

But Bruce made for the front lawn where he extruded a large turd. Frank had to stand by and stare into the distance, so to speak.

On his second day, Frank came to the courtyard. Bruce walked him to the center. There, to my lasting gratitude and wonder, he bumped into Trevor.

“Watch where you’re going!” Trevor boomed.

There was complete silence in the courtyard as Frank regained himself.

“Can’t you see I’m blind,” he snapped.

Trevor grabbed Frank by his shirt.

“Look,” he boomed, “that’s not funny!”

“Of course it isn’t funny!” Frank retorted and wrestled with Trevor’s hand. “I’m blind!”

Trevor let go of his shirt.

“I’m blind too,” he boomed.

For a few seconds, neither of them said anything.

“You sound deaf,” Frank remarked.

They stood together for a while longer and then Trevor prodded Bruce with his cane.

“What’s that?” he asked.

“What?”

“That thing you’ve got there?”

Frank bent down and discovered the cane. He pushed it aside and was led away by Bruce.

“Hello?” Trevor boomed. “I say—”