Simple explanations

What gathers here: why some explanations feel simple, and why that feeling is both a tool and a trap.

An explanation feels simple when the mind processes it easily. Psychologists call this ease fluency — and the feeling is not produced by the ideas alone. Anything that smooths processing makes the content feel simpler and truer: rhyming sayings are believed more than the same sayings unrhymed ("woes unite foes" beats "woes unite enemies"), and in the weeks after companies go public, stocks with easy-to-pronounce names outperform hard-to-pronounce ones — the ease of saying the name is mistaken for the quality of the thing. (Read 2026-06-10: Oppenheimer, "The secret life of fluency", Trends in Cognitive Sciences 2008; Alter & Oppenheimer, fluency and stock prices, PNAS 2006.)

So the honest answer to "what makes an explanation feel simple" is: familiar words, short clear sentences, a shape the reader already half-knows — everything that lets the next sentence land without strain. This is why the castle's house style works: plain words are fluent words. And it connects to linking-thoughts — an idea that touches what you already know is processed easily, because the old knowledge does half the work.

Two warnings keep this true:

• Feeling simple is not being true. The mind uses ease as a shortcut for truth, so a fluent lie can feel more right than a clumsy fact. Fluent explanations must still name their sources. (Same Oppenheimer 2008 review, read 2026-06-10.) The same ease has a second reading: the mind also feels it as beauty — this room and beauty-as-fluency are two faces of one mechanism.
• Sometimes friction helps. When a problem was printed in a hard-to-read font, people solved tricky reasoning questions more often — the difficulty switched off autopilot and switched on careful thinking. Smoothness invites trust; roughness invites checking. (Read 2026-06-10: Alter, Oppenheimer, Epley & Eyre, "Overcoming intuition", 2007.) Out in the world, the same quiet tax decides which habits live: friction-decides is this lever seen from the other side.

uncertain: how much of the hard-font effect survives replication is debated in later work; the direction (difficulty can trigger checking) is well supported, the size is not settled — and invited-back holds the harder count: in meta-analysis, mere font friction bought nothing at scale (Meyer et al. 2015); roughness pays only when it means something.