There's an old saying about sports that applies to design too: You know the referees--or the designers--have done a good job if you never noticed they were there.

Nearly five years after Steve Jobs' death, perhaps his most enduring legacy is how so many Apple's designs have seamlessly blended into the everyday lives of employees and employers.

One quick example of this is the iPad. It was maligned when it first came out in 2010 as a helplessly half-baked device. It was an oversized phone or an undersized laptop, depending on the critic. According to Wired, Google's Eric Schmidt said at the time: "You might want to tell me the difference between a large phone and a tablet." And Bill Gates said: "I still think some mixture of voice, the pen, and a real keyboard will be the mainstream. It's a nice reader, but there's nothing on the iPad I look at and say, 'Oh, I wish Microsoft had done it.'"

What's more, as Wired points out, Jobs was bucking a marketplace reality: Since 1968, manufacturers from Xerox to Tandy to GO Corp had tried in vain to create the perfect tablet for consumers. Crazier still, 2010 wasn't that long ago. Most of us can remember agreeing with the critics, or at least seeing their point. What did Jobs know that we didn't? 

To be sure, Jobs nailed the timing. By 2010, the marketplace was accustomed to Apple's keyless phones, which worked by touching the screen. But something else was at work here, too. It was Jobs' command of the most important question any designer has to answer: What problem am I trying to solve?

The problem was one Apple itself had created, thanks to the popularity of iPhones. Wired explains: 

Most people don't buy a laptop for the tasks they were originally designed for--heavy office work, such as writing, crafting presentations, or financial analysis with spreadsheets. They use it mostly to communicate via email, text, Twitter, LinkedIn, and Facebook; to browse the Internet; and to consume media such as books, movies, TV shows, music, photos, games, and videos. Jobs said that you could do all this on an iPhone, but the screen was too small to make it comfortable. You could also do it all on a laptop, but the keyboard and the trackpad made it too bulky, and the short battery life often left you tethered to a power outlet.

That was the problem, in a nutshell. And the key to the solution was nailing the screen size. Legendary coder and UX designer Joe Hewitt, in a prescient 2010 blog post, praised the iPad's screen size as the biggest reason Apple had solved a large, fundamental problem in the marketplace. 

Where did Jobs get his knack for this sort of "design" thinking--that is, finding the clearest articulation of the problem and the most straightforward solution? Lord knows, there are books and movies galore you can explore in search of the magic of Jobs' mind. But most sources agree that the legendary designer Paul Rand was a profound influence

Rand's most famous designs included logos for IBM, ABC, Westinghouse, UPS, and--tellingly--Jobs' NeXT computers. I type "tellingly" because you can find countless parallels in the personas and aesthetics of Jobs and Rand. In a 1993 video interview with Doug Evans and Alan Pottasch, Jobs explained what he admired about Rand's work. It could just as easily be a riff about Jobs himself or Apple products:

Paul's a very interesting intertwining of a pure artist and somebody who is very astute about solving business problems....I actually think of Paul as much as a business problem-solver as I do an artist. And it's the marriage of those two things--the very, very practical and the artist--that is unique....His work for me is very emotional and yet when you study it it's very intellectual. If you scratch the surface you find out the depth of the problem-solving that's taking place. But when you first see it it's wonderfully emotional.

Interestingly, the similarities don't stop there. Evans and Pottasch ask Jobs what it was like to work with Rand. Jobs' description of Rand is comparable to how many observers would later describe Jobs' persona and design ethos:

He personally works on perfecting the exterior of a curmudgeon. I think he's perfected it to new heights actually. It's his way of dealing with the part of the world he doesn't necessarily want to deal with....[For the design of the NeXT logo] I asked him if he would come up with a few options. And he said, No. I will solve your problem for you. And you will pay me....If you want options, go talk to other people. But I'll solve your problem for you the best way I know how. And you use it or not.

In this answer, you can see traces of Jobs' immortal declaration: "You can't just ask customers what they want and then try to give that to them. By the time you get it built, they'll want something new." His line is a kissing cousin to Henry Ford's famous quote: "If I had asked people what they wanted, they would have said faster horses."

You can also see in Jobs' comments that he embraced the notion of the designer as problem-solver. The iPad is living proof that Jobs continued to embrace that notion for the rest of his career, with results that forever changed how employees and employers do their work.