Ethereum’s “Ship of Theseus”

Text/Chang Jian

If Zhang San owes you money, and many years later, Zhang San uses cloning technology to copy himself and says that the clone is Zhang San, the original Zhang San's debt relationship will be invalidated. The clone looks almost the same as Zhang San, but his memory is completely different. He does not admit to knowing you at all, let alone owing you money. In this case, would you beat Zhang San up, take him to the police station, and accuse him of hooliganism?

Now, such a blatant "hooliganism" has occurred in the blockchain community. Not only did it not cause public outrage, but it was praised as the conscience of the blockchain development team and a model for the development of blockchain applications. Yes, I am talking about the Ethereum hard fork incident. By modifying the code of the Ethereum software, all funds of The DAO and its sub-DAOs were forcibly transferred to a specific refund contract address at block 1920000, thereby "taking back" the coins of the DAO contract controlled by the hacker.

Whether the Ethereum hard fork is successful depends on an ancient philosophical question: The Ship of Theseus. The Ship of Theseus first appeared in Plutarch's records. It talks about a ship that can sail on the sea for hundreds of years. During the voyage, it is continuously repaired and replaced with parts until every part of the hull and every deck is replaced. Then, is the repaired ship still the original Ship of Theseus? If we go a step further and use the old parts taken from the Ship of Theseus to rebuild a new ship, which of the two ships is the real Ship of Theseus?

In fact, in real life, we are not troubled by the "Ship of Theseus". For example, our bodies are made up of elementary particles and cells, and they have been metabolizing non-stop since the day we were born. The human skin epidermis is renewed on average every 3 weeks, liver cells are renewed on average every 5 months, and the most stable bone tissue only needs 10 years to be renewed. The cells and elements that make up your body today are very different from those yesterday, and almost completely different from those a few years ago. But we still think that you are still you, and you are the same person now as you were a few years ago. Why is this?

Obviously, the essence of things does not depend on the organization and structure that constitutes it, but on its function and continuity of time and space. Laozi explained the Ship of Theseus in the Tao Te Ching more than 2,000 years ago: " When clay is molded into a vessel, it is the hollow part that makes it useful. When windows and doors are cut to make a room, it is the hollow part that makes it useful. Therefore, what is there is benefit, and what is not there is useful ." This means that when clay is kneaded into a vessel, it is the hollow part inside the vessel that makes it useful. When windows and doors are cut to build a house, it is the hollow part inside the four walls that makes it useful. Therefore, the solid part (the material of things) brings convenience, but it is not the function itself. The empty part is the essence of things, that is, its function. The reason why a bowl is a bowl depends on its function of holding things, not its material (wood, clay, pottery, metal). Although all the parts of the Ship of Theseus have been updated, the passengers on the ship are still the same passengers. After buying the tickets, the passengers establish a contractual relationship with the Ship of Theseus. This contractual relationship will not be transferred to another ship. The ship still serves the passenger transport function of transporting passengers from the departure port to the destination port.

The blockchain is such a Ship of Theseus, which is constantly updated during the voyage. Here is a video that vividly demonstrates the development trajectory of the Bitcoin Satoshi client: https://youtu.be/PfKlee8kLE4. Perhaps at the beginning, the Satoshi client was just a pile of scrap metal and a pile of logs. We can call them "Ship of Theseus.v.0.0.0.0", and then after a period of construction, it has a preliminary ship shape, so it can be called "Ship of Theseus.v.0.0.0.1"... In the future, it will be iterated to "Ship of Theseus.v.27.78.1.0". Today's Bitcoin code is completely different from Satoshi's version, but we have never had cognitive confusion. Why is this? The reason is simple. We have been following and using the transaction data accumulated in the history of Bitcoin today. These transaction data are the passengers of the blockchain ship. Since the genesis block, the transaction data has established a contractual relationship with the Bitcoin client, and these transaction data have never been tampered with in history.

The Ethereum hard fork and the Bitcoin version update are two completely different things. The former used the old parts taken from the ship of Theseus to rebuild a new ship, but tampered with the passenger list and claimed that this was the ship of Theseus. It turned out that the ship did not disappear as the developers imagined, and it was still sailing on the original route. So there are two almost identical ships, except for the different passengers, and the future routes may also be different.

Which one is the real Ship of Theseus? The answer is self-evident. If the soft fork of the version is like the metabolism of the human body, then the hard fork is like the gene cloning of the human body. The body cells of Zhang San who owed you money seven years ago may have been completely renewed, but Zhang San is still Zhang San, and your debt relationship, social relationship, and shared memory still exist. But if Zhang San clones himself and tries to transfer the debt relationship to the clone, you, the court, and society will not recognize this transfer of identity.

So, was the Ethereum hard fork successful? Yes, it was successful, and it just confused the public. But as the great man said, you can't fool everyone all the time, and the bankruptcy of this behavior of calling a horse a zebra is foreseeable. After the Ethereum hard fork, many friends who didn't know the truth asked, isn't it said that the data on the blockchain is irreversible and cannot be tampered with? Why can Ethereum be changed? Here I want to clarify that although the computing power of the Ethereum blockchain is not as exaggerated as that of Bitcoin, the data of the Ethereum blockchain is still tamper-proof, but they call the correct data ETC.

Some friends also argued that " the essence of the proof-of-work mechanism is that computing power is power. Since the longest chain contains the largest amount of work, the longest chain is the most legitimate chain. ETH's computing power is much greater than ETC, and the height of the ETH blockchain is much higher than that of ETC, so ETH is the most legitimate chain. " This is another form of stealing concepts. It is true that the longest chain is the most legitimate in the proof-of-work, but the premise is that these miners are mining the same version of the block . For example, if someone releases a hard fork version of Bitcoin and changes the block generation speed to 1 block per minute, then the generation speed of this new version of the blockchain will far exceed the original chain. Can this new version be said to be more legitimate?

The only legitimate way to modify blockchain data is a 51% attack. Can the Ethereum authorities do it? Obviously, they can't. But they are very good at gene cloning. It is not difficult to imagine that if there is one gene cloning, there will be a second and third time. The Ethereum community has already split into two forces. This is a bit like the game of life of cellular automata (note [1]): every 4 turns, the "glider" will move one square to the lower right corner. Although the cell is already a different cell, it can maintain its original shape. The "spray gun" will continuously release one glider after another. This is a perfect simulation.

Glider

spray gun

Finally, let me tell you a joke. A, B, C, and D are discussing "Can the Ethereum official modify the blockchain?"
A: What is blockchain?
B: What do you mean by official?
C: What is modification?
D: Which Ethereum?

Note [1]: The model proposed by von Neumann in the 1950s, in which each cell scattered in a regular grid takes a finite number of discrete states, follows the same action rules, and is updated synchronously according to certain local rules. This constitutes a cellular automaton.