Vertical vs. Lateral: Two Ways to Dig

Last lesson we met the truck stuck under the bridge, and the one-line fix: let the air out of the tyres. Everyone frantically re-measured the bridge (dig the same hole deeper); one person dropped the truck (dig a new hole). We gave that split a name — vertical vs. lateral thinking — and a picture: dig one hole deeper versus start a new hole somewhere else.

That picture is memorable. It’s also, so far, a slogan. This lesson turns it into something you can actually use: a precise definition of each mode, worked examples, and — the part that pays rent — a reliable sense of which mode the moment is asking for.

Let’s start by feeling the split before we name its parts.

Hold onto that feeling of the sideways jump. Now the definitions.

Vertical thinking: dig one line, carefully, all the way down

Vertical thinking is the mode you were trained in at school, and it is most of useful thinking. Picture a miner sinking a single shaft: pick a spot, and go straight down — each swing of the pick landing where the last one left off, every layer checked before you dig through it.

Precisely, vertical thinking is:

• Sequential — each step follows from the one before. You move down a line.
• Justified at every step — you don’t proceed until the current step is right. A wrong step is a wasted step, so you reject it.
• Selective — it’s a filter. At each fork you judge the options and keep the best one, discarding the rest. It says “no” a lot, on purpose.
• Single-line — it commits to one hole and deepens it. Depth is the goal.

Its home turf is anywhere correctness compounds: analysis, logic, mathematics, and execution. When the path is roughly known and the job is to walk it flawlessly, vertical thinking is exactly the tool.

Worked example: bisecting a bug

Your app worked on Monday and is broken on Friday. Between them are 200 commits. Vertical thinking, textbook style:

1. Pick the commit halfway through — commit 100.
2. Check out that version. Does the bug exist? Say no.
3. So the bug entered in the second half (commits 101–200). Discard the first half entirely.
4. Take the halfway point of what’s left — commit 150. Test. Bug present? Yes.
5. Discard commits 151–200. Repeat on 101–150.

Each step is justified (you tested, you didn’t guess), sequential (each test narrows the last range), and ruthlessly selective (half the commits get thrown out every round). After about 8 tests you’ve pinned the exact culprit among 200. That is vertical thinking working beautifully — and no amount of “creativity” would beat it here. The line was the right line; you just had to walk it well.

The pitfall: vertical thinking is superb at digging and terrible at noticing it’s in the wrong spot. Because every step is locally justified, a perfectly-executed shaft can bottom out in bedrock — technically flawless, and pointed at nothing. “We optimised the page for a week” is 200 correct swings of the pick in a hole that was never going to reach water. The mode has no built-in alarm for wrong place; only for wrong step.

Lateral thinking: move sideways to a different starting point

Lateral thinking is the deliberate move to a different place to start digging. Where vertical goes down, lateral goes across — to a new position from which a new, possibly better, shaft can be sunk.

Its rules are almost the mirror image of vertical’s:

• Generative, not selective — its job is to produce new starting points and framings, not to judge them yet. It says “yes, and” where vertical says “no, but.”
• Provisional / allowed to be “wrong” — a lateral step doesn’t have to be correct in itself. It can be a stepping-stone you’ll later kick away. Being right at each step is not the point.
• Concerned with change, not truth — its target is a new way of looking, not a proven conclusion. Success is a fresh angle, and you hand the “is it actually right?” question to vertical thinking afterwards.

Note that last one carefully, because it’s the piece that trips people up: within lateral thinking, being logically correct at each step is not the goal. The goal is movement — getting to a viewpoint you couldn’t have reached by careful downward steps.

Worked example: the slow elevators

A classic. An office building gets a flood of complaints: the elevators are too slow, people wait forever, tenants are threatening to leave. The vertical line is obvious and expensive — make the elevators faster: new motors, better scheduling algorithms, maybe an extra shaft. All of it is correct engineering. All of it costs a fortune.

The lateral move changes the starting point. Instead of “the elevators are too slow,” ask: what’s the actual complaint? People hate the wait. And you don’t have to make a wait shorter to make it bearable — you can make it not feel like waiting.

The fix: mirrors (and, later, screens) by the elevator doors. People check their hair, glance at the news, and the felt wait collapses. Complaints vanish. Cost: trivial. The elevators are exactly as slow as before.

Watch how that violated vertical’s rules and won anyway. “Make the wait feel shorter” is not a deeper step down the “make it faster” shaft — it’s a different shaft. And on the way there you had to entertain a provisional, almost silly reframe (“the problem isn’t speed, it’s boredom”) that a strict step-by-step check might have rejected as off-topic. That permission to not be right at each step is exactly what let the sideways jump happen.

The pitfall: beginners hear “provisional, not-necessarily-right” and conclude lateral thinking means anything goes — brainstorm nonsense and call it genius. Not so. Lateral thinking generates candidate starting points; it does not get to skip the part where vertical thinking then checks whether the candidate actually holds up. The mirror idea felt like magic, but it only counted because it worked under scrutiny. Lateral without a vertical follow-through is just daydreaming.

Why willpower keeps you in the groove

Last lesson we said the brain is a self-organising pattern system — like rain landing on a hillside and, over time, carving channels that later rain then follows. Let’s go one notch deeper, because this is why you can’t just “try harder” your way to a sideways idea.

The channels are asymmetric. Once a groove exists, it is very easy to fall into — the ball of your attention rolls into it with no effort at all. But it is very hard to climb across from one groove to the neighbouring one, even when the neighbour is the better route. Downhill into the familiar pattern: free. Sideways into a different pattern: uphill, against the terrain.

This asymmetry is the secret behind two things that feel unrelated: humour and insight. Consider a joke. The setup rolls your mind smoothly down the expected groove; the punchline suddenly drops you into a different groove you didn’t see coming — and the instant you land there, you realise you could have gotten there all along. That “oh!” and the laugh are the sound of a sideways jump between patterns. It’s also why a good punchline feels obvious in hindsight: from the new groove, the path back is downhill and easy, so of course it looks inevitable now.

Insight — the “aha” of a clever solution — is the exact same jump, minus the comedy. The elevator mirrors are a punchline: absurd for a split second, then obviously right.

Worked example: the obvious-in-hindsight test

Every good lateral solution passes a specific test: before, it seems irrelevant or wrong; after, it seems so obvious you’re mildly annoyed you didn’t see it. Let the air out of the tyres. Put up a mirror. Show a skeleton screen. Each one is a groove you were sitting right next to the whole time and couldn’t cross into — until something bumped you across.

The pitfall: because the answer looks obvious afterwards, people conclude they could have just thought harder to reach it — and so they refuse to learn any technique, insisting effort is enough. But the whole problem is that effort flows downhill, deeper into the groove you’re already in. Willpower is horsepower, and horsepower only makes you dig your current hole faster. To jump across grooves you need something that deliberately points you sideways — which is precisely why the rest of this course teaches tools, not pep talks.

They divide the labour: a relay, not a rivalry

Here’s the reframe that makes the whole thing click. Vertical and lateral thinking are not two opposing teams. They’re two legs of a relay race.

• Lateral runs the first leg: it generates candidate starting points and fresh framings. Its output is options — “we could look at it as X, or Y, or the weird Z.” It does not build anything; it opens doors.
• Vertical runs the second leg: it takes the most promising framing and tests it, develops it, and builds it out — the careful downward shaft that turns a fresh angle into a working solution.

Lateral finds the better hole; vertical digs it. Neither wins the race alone. The elevator story is the relay in miniature: lateral hands over “make the wait feel shorter” (leg one), and vertical then works out which distraction, where to place it, what it costs (leg two). Skip leg one and you dig the wrong hole flawlessly. Skip leg two and you’ve got a cute idea and no elevator.

Now sort some moves so the split stops being abstract:

The pitfall — and it’s the big one: people mistake these two modes for two personalities. “I’m a creative type.” “I’m a logical person.” As if lateral and vertical were tribes you’re born into. They’re not. They’re modes anyone can switch between, like walking and running — nobody says “I’m a walker, so I can’t run.” Mastery isn’t picking a side; it’s knowing which mode the moment calls for and switching cleanly into it. The “logical person” who refuses to reframe is just someone stuck digging, and the “creative” who never checks their idea is just someone daydreaming. Real skill is fluency in both legs of the relay.

When to switch modes

Fluency is worthless without timing. So here are the two signals — one for each direction.

Switch to lateral when the obvious direction stops paying off. Two symptoms:

1. Diminishing returns. More effort in the same line buys less and less. The slow page: optimise, cache, upgrade — each helps a bit, then plateaus. When the pick keeps landing and the hole barely deepens, you’re in bedrock. Stop digging down; go find a new spot.
2. Technically right, but unsatisfying. You’ve reached an answer that survives every check and still feels wrong — expensive, ugly, or beside the point. “Make the elevators faster” is correct. It also costs a fortune and misses what people actually hate. That itch of a correct-but-hollow answer is lateral thinking’s cue to look elsewhere.

Switch back to vertical when you’ve got a promising new angle and need to make it real. The moment lateral hands you a framing that smells right — “make the wait feel shorter” — the generating is done. Now the job is to develop and test it: which distraction, where, at what cost, does it survive scrutiny? That’s a downward shaft, and it’s vertical work. Keep brainstorming past this point and you’ll collect a pile of angles and build none of them.

Recap

Where this goes next

You can now tell the two modes apart on sight, feel the moment the digging stops paying off, and know that the fix is a sideways move — not a harder one. But “move sideways” is still a direction, not a method. How do you actually cross to a better groove on purpose?

Lesson 3 — Reframing & Hidden Assumptions — teaches the single most reliable lateral move there is: finding the unspoken assumption that’s quietly holding the problem shut, and deliberately dropping it. Almost every “obvious in hindsight” solution turns out to be an assumption someone finally stopped making. Next, we learn how to hunt those assumptions down on command.