Final answer:
Thomas Hobbes is the philosopher who posited the concept of a 'Leviathan' or a strong centralized authority to prevent a 'state of nature', essentially a state of war and anarchy. So the correct answer is Option A.
Step-by-step explanation:
The thinker who posited the need of a 3rd party government named 'The Leviathan' is Thomas Hobbes. Hobbes' theory, as detailed in his work 'The Leviathan', centers on the idea that human beings are fundamentally and universally selfish and that their actions are motivated solely by self-interest. In order to prevent a 'state of nature', which Hobbes views as a state of war and anarchy, a strong centralized authority or 'Leviathan' was necessary to maintain law and order.
Learn more about The Leviathan