Part 0 · Why Bitcoin Exists

You cannot appreciate a single line of Bitcoin’s design until you feel the problem it solves in your bones. So before any cryptography, blocks, or mining, we spend Part 0 making the problem hurt. Everything Bitcoin does afterward is machinery in service of solving it.

The one-sentence story

The three big chains are a story of escalating ambition:

money → programmable money → fast programmable money

Bitcoin is the first word. It answers a question nobody could answer for ~30 years: can we have digital money without a trusted middleman?

The recurring question

Tape this to your monitor. For every mechanism we meet in this entire course, ask:

“How does this help untrusting strangers agree on one ledger?”

Hashes, signatures, blocks, mining, halvings — every one of them is an answer to that question.

What this part covers

1. What money actually is — why money is, at its core, a shared ledger.
2. The double-spend problem — why naive digital cash fails.
3. The trust problem — why the obvious fix (a bank) is not good enough.
4. Byzantine generals & Sybil attacks — the two deep obstacles.
5. The predecessors — DigiCash, Hashcash, b-money, bit gold, and what each lacked.
6. Satoshi’s synthesis — the single insight that tied it all together.

The full syllabus

Part 0 is the why. The rest of the course is the how, in dependency order:

Part	Topic
0	Foundations — why Bitcoin exists
1	Cryptography — hashing, keys, signatures, Merkle trees
2	Transactions & the UTXO model
3	Blocks & the blockchain data structure
4	Consensus — Proof of Work & mining
5	The network & node types
6	Economics & incentives
7	Wallets & keys (BIP32/39/44)
8	Modern Bitcoin — SegWit, Taproot, Lightning
9	Hands-on — run a node, read the chain

How to use this course

Read in order. After each page, answer the Check your understanding prompts in your own words before moving on — explaining it back is what turns reading into knowing.