Reasoning & Proof.

The cross-domain cousin of Euclid Lab. The geometry is incidental; what carries is the habit of asking what licenses each step. This path uses two essays and a diagnostic to install that habit somewhere it can travel.

Five steps · roughly two weeks · vocabulary first, then practice.

• № 01 · Concepts
  Justification, dependency, common notion

  Fix the vocabulary first. The terms below — justification, dependency, postulate, definition, common notion — are doing real work in everything that follows. Reading the entries before the essays makes the essays sharper.
  8 min · glossary
• № 02 · Read
  Training the Ability to Be Less Easy to Fool

  On calibration, counterexamples, and the underrated discipline of doubting one's own fluency. The argument is that most people overrate how much they know — and that this is fixable, but not by reading more.
  13 min · essay
• № 03 · Diagnose
  Counterexample challenges

  Five short proofs, each with exactly one invalid step. The exercise is not to recognise the error but to name what would license the legitimate move instead. Calibration is built by the second move, not the first.
  20–30 min · tutor
• № 04 · Read
  Productivity Is Not Enough

  A quiet quarrel with the contemporary cult of throughput, and an argument for a different metric: durable capability. Read this last; the diagnostic gives it teeth.
  10 min · essay
• № 05 · Transfer
  A claim of your own

  Pick a confident claim you made in the last week — work, writing, conversation. Write down the chain of reasoning that supports it. For each step, name what licenses the move. The point is not to find an error; the point is to discover whether the chain has steps at all.
  15 min · offline