Availability is a security issue. Machines that cannot perceive the real world can only be used as tools and cannot solve security issues in the real world. For example: If the autonomous vehicle cannot perceive the availability of the road in the real world, then the automatic driving of the vehicle must be unsafe. The roads in the real world are constantly changing, and cars cannot perceive the complex and ever-changing real world. Therefore, cars have no usability, and it is unsafe to insist on using them. Similarly: Formal blockchain industry, if a public chain cannot perceive the real world, then the public chain is unusable, and naturally the public chain is insecure. reason: G ö del's incompleteness theorem proves that any single formal system is incomplete, closed, and cannot solve self referential problems. Solution: Find the self referential interfaces of each individual formal system, and use the nonlinear logic of P/NP to combine them into an emerging nonlinear adaptive whole of multiple formal systems interconnected with each other. Use case: Bitcoin The miner for computing nonce in Bitcoin is a type of formal system that allows 1 to infinite entity miners formed by this type of formal system to compete for solving nonce in a block simultaneously. This is a formal system for the difficulty of solving P/NP problems. The longest chain is the foundation of the distributed ledger UTXO, as well as the self pointing interface of the distributed formal system miner, and the formal system for verifying the P/NP problem of the distributed formal system miner. And the longest chain is an intuitive assumption, assuming that 51% of loyal nodes will generate the longest chain. Thus, the self referential problem of G ö del's incompleteness theorem was solved using intuitive assumptions. Final result: Bitcoin links two types of formal systems, P/NP difficult to solve and easy to verify, through intuitive assumptions (named by Turing as oracle machines), thus giving rise to nonlinear adaptive systems, which perceive the real world in formal systems with P/NP difficult to solve and have value in formal systems with P/NP easy to verify. Thus, it has become an organic whole that is unified with human nature, namely the human-machine symbiotic system.