How did Steve Jobs apply first principles thinking to break the 'keyboard phone' paradigm during iPhone design?

Haha, that's an interesting question. I think it can be understood this way:

Imagine what kind of phones we used before the iPhone came out? Nokia, BlackBerry – they all had a dense array of physical buttons below the screen. At that time, all phone manufacturers, and users alike, thought this was how a phone should be. Want to make it better? That meant making the keyboard feel more comfortable or the buttons more powerful. This was 'inertial thinking,' much like how people in the past believed that to make a carriage faster, you needed stronger horses, rather than considering inventing an automobile.

But Steve Jobs, he approached problems differently. He liked to 'tear down the house to its foundation and then see if those bricks could be used to build a completely different kind of building.' This is what's known as first principles thinking.

He didn't ask, "How can we design a better physical keyboard?" Instead, he went back to the most fundamental questions:

1. What is the core of a phone? It's a screen, used to display information (web pages, photos, videos).
2. What do we need to do with the phone? We need to interact with what's displayed on the screen (input commands, type).
3. So, what's the most direct and efficient way to interact?

The answer at the time was: through a physical keyboard. But Jobs thought this was foolish. A physical keyboard is fixed; it always occupies half the phone's area. Yet, you only need it when typing. When watching videos, playing games, or viewing photos, it becomes an annoying burden.

So Jobs thought, humans are naturally equipped with the best pointing tool – our fingers. Why can't we directly tap on things on the screen with our fingers?

This idea was quite radical at the time, because touchscreen experiences back then were terrible; they were single-touch only and very inaccurate. But Jobs was convinced this was the right direction, believing that "directly touching content with your fingers" was the most intuitive way to interact.

Consequently, Apple tackled the technical challenges and created the revolutionary "Multi-Touch" screen.

You see, with this, the whole logic falls into place:

• Discard the physical keyboard: The front of the phone could be one massive screen, offering an extremely powerful visual impact.
• Keyboard becomes software: When you need to type, a virtual keyboard pops up on the screen; when you don't, it disappears, returning the space entirely to the content itself.
• Brand new interaction: Because of multi-touch, you could easily pinch to zoom in and out on photos and web pages with two fingers. This kind of experience was simply impossible with a physical keyboard.

So, to summarize: while everyone else was thinking "how to improve the horse-drawn carriage," Jobs was asking, "What is the purpose of my travel? It's to get from A to B faster." Starting from the most fundamental need of "interacting with content," he found the most direct solution: "fingers + touchscreen." This led him to eliminate the cumbersome physical keyboard and design the iPhone, a "new species" of device. He wasn't just moving faster on the old path; he directly forged a completely new one.