2. Timechain Consensus: Chronos meets Kairos
Blockchain transactions exist in space and time. The former being the space in the block it is included in, of the chain that such a block is further part of, of the space of the validation logic that legitimizes it to be even considered by the validators/proposers/blockbuilders for inclusion in the current block. The temporalities of blockchain transactions can be expressed in the lifecycle of every transaction in terms of the following three modalities:
- Past Tense: Confirmed transactions permanently recorded on the blockchain. They remain in the past frozen, impossible to be tampered with as are all things past, as operating under the immutability logic of ever deepening cumulative confirmation by consensus.
- Future Tense: Pending/proposed transactions in the mempool awaiting inclusion in a block. All transactions and requests for transactions once left the wallet and user apps being broadcast node to node as they await to be picked up by searchers/builders/proposers to be worked. In the mempool they remain as potentialities for a future where they might be confirmed.
- Present Tense: The transitional time between past and present when transactions are being executed in an effort to confirm them onchain. This is the time when transactions are being picked up, searched/solved, validated and bundled/sorted into blocks by miners or validators/proposers.
As per Nakamoto consensus, the unwritten law of the present tense was that, as long as they are valid transactions, a miner should give them priority for inclusion based only on the amount of transaction fees they pay, informally prohibiting other attempts to interact with the transactions as amounting to tampering the sanctity of temporal purity. "Replace-by-fee" was a controversial Bitcoin soft protocol change, allowing transactions that are in the mempool or already in miners' blocks to be replaced by other mutually exclusive transactions that pay higher fees. That could lead to miners reading the contents of the transactions and selecting new transactions based on their preferred UTXO update or worse leading to censorship. Miners had to act in a passive way, never actively interacting with transactions, just follow the fee based allocation of blockspace for valid transactions, adding no flavor of their own.
This assumption that miners were passive actors during transaction execution changed for the first time with MEV on Ethereum: ETH miners started interacting with the blockspace by manipulating the order of transactions, giving preferential inclusion to low latency traders who were competing for arbitrage and other trading opportunities by "tipping" or "bribing" miners directly for inclusion. With MEV, miners transitioned from passive to an active mode in the present tense modality of transaction lifecycle. MEV remains to be most radical (change) departure in the temporality of transaction lifecycle in the life of the "timechain" [Nakamoto]. Thus, we get two further delineations under the Present Tense modality of our three transaction temporalities:
- Present Passive: Transactions are executed without any significant third-party interpretation of their internal or implicit semantics beyond validity and transaction fees. This was the only mode of temporality as per Nakamoto Consensus.
- Present Active: Transactions are executed after an extensive search over different possible inclusions in different bundles with other third-party transactions, not simply based on their own independent validity and transaction fees paid. In the case of trades/swaps these bundles typically include the transactions of adversary traders, or of the miner/proposer themselves. This mode of temporality was made possible solely due to MEV.
| Past | Present | Future | |
|---|---|---|---|
| Passive | Confirmed Tx | Nakamoto Miners / Proposers in PBS | Mempool Tx |
| Active | BTC Scripts | Validators carrying out MEV themselves | Searchers |
Table 1
2.1. Current Attempts To Fix The Timechain
MEV represents a major disruption in the temporality of blockchain transactions. Analysts and engineers are trying to find solutions that will get rid of MEV or to wind back the clock on blockchain transaction semantics. This is focused around the framing that MEV resulted in the concentration of powers among and around validators since it made them become the only actors to benefit from the dual power of being able to be in the present tense and also in the active mode of interacting with transactions. To mitigate this in an effort to ensure fairness, Vitalik and Flashbots introduced a new set of actors, elaborating that of bundle searchers into “builders” along with turning validators into what they are called now “proposers” as is in the name: Proposer-Builder-Searcher.
In PBS, the powers of proposers (erstwhile validators) now supposed have been reset back being only in the present tense (so present passive), as was the case with Nakamoto consensus, by restricting proposers to only be able to engage via a block builder auction. PBS leaves the proposers with neither the power to build blocks nor to select/organize transactions, while the searchers/solvers are now wholly responsible with the power to actively interact with transactions. So leaving only builders and searchers as active participants but not present, as actively interacting with transactions in a pre-chain way.
MEV, as an intervention with respect to the temporality and the timing of blockchain transactions, has been largely ignored by the more prevalent rhetoric of MEV being about trading profits/losses, greed, and fairness. Even when the current dominant attempts at addressing the issues of MEV was about decoupling the transaction temporalities via PBS, this aspect around time still remains largely underdeveloped or rarely explicated in technical analytical terms.
| Temporality (about states) | Timing (about relationships) |
|---|---|
| Past—Present—Future | Before—After (and Now, not so much as the midpoint insofar as it is the double negation: as neither before, nor after) |
| Confirmed—BeingMined—Mempool | Order of Transactions |
| Present creates the Past/Future | Before-After creates the Now |
| Subjectivity (there is no present tense without a subject being present) | Objective (before-after relations are agnostic to subjective experience) |
| Immutability | Time Travel |
| Block (Re)-Ordering | Transaction (Re)-Ordering |
Table 2
Please note that we have been talking about two different notions as it regards to time. The past, present and future tenses represent the modalities in the transaction lifecycle. This is not to be confused with the time travel reference made earlier when transactions and internal transactions make calls to the future (within the same block/bundle) for return values and calls to be returned, and this operates under the relationship of before-after (and now). So the two notions are: past-present-future, and before-after-now. The former speaks of temporalities, while the latter are notions of (time in terms) of timing, so we have temporality versus timing. This is akin to the Hellenistic Greek notions of Chronos versus Kairos.
(The differences between the notions of Temporality and Timing carries with it significant similarities with McTaggart’s notion of A series versus B series as explicated in his 1908 paper, “The Unreality of Time,” [source] in that only the A series has tense as in a universe with subjects experiencing the time, while the B series lacks any sense of tense as in a block universe.)