Wittgenstein's ladder

ウィトゲンシュタインのはしご

Gödel's incompleteness theorems – Limitative results in mathematical logic

Kōan - koan -- Story, dialogue, question, or statement used in Zen practice

lie-to-children – Teaching a complex subject via simpler models

Neurath's boat – Philosophical analogy about knowledge

Russell's paradox – Paradox in set theory