Step 1: John Austin's Theory Explained.
John Austin, a proponent of legal positivism, posited that law is essentially the command of a sovereign. His theory, known as the "command theory," defines law as the expressed will of a sovereign, enforced by the state's power through potential sanctions.
Step 2: Evaluating the Options.
- (1) Hugo Grotius: Grotius's work centered on natural law, not the command of a sovereign.
- (2) John Austin: Correct. Austin's command theory identifies law as the sovereign's command.
- (3) Jean Bodin: While Bodin stressed sovereignty, he didn't define law solely as a sovereign's command.
- (4) Thomas More: More focused on utopian concepts, unrelated to legal positivism.
Step 3: Determination.
The correct choice is (2) John Austin.