[CryptoPunk]

>>authorized by law to act as a single person,

This can be common law, recognizing the legal authority the shareholders grant the corporate entity to act on their behalf.

There is a common law justification to treat that entity as a legal person because it acts as a single entity, as willed by the shareholders.

I am not suggesting that the corporate legal structure has never come into existence by legislation. I am just saying that the corporate structure can also emerge entirely through the common law enforcement of contracts.