In political theory, who among the following thinkers is best known for propounding the monistic theory of sovereignty?

Introduction / Context:
The concept of sovereignty is central to political science and constitutional theory. Different thinkers have offered various explanations of who or what holds supreme power in a state. The monistic theory of sovereignty holds that sovereignty is absolute, indivisible, and resides in a single determinate authority. This question asks you to identify the thinker most famous for advocating this monistic, legalistic view of sovereignty.

Given Data / Assumptions:

• The focus is on the monistic theory of sovereignty.
• The options list John Austin, Charles Darwin, Aristotle, and Karl Marx.
• You must choose the thinker whose political theory clearly reflects a monistic, legal understanding of sovereignty.

Concept / Approach:
John Austin, a nineteenth century legal philosopher, is known for his command theory of law, in which laws are commands issued by a sovereign and backed by sanctions. For him, sovereignty is indivisible and resides in a determinate human superior who is habitually obeyed by the bulk of the population and does not habitually obey any other human superior. This is a classic example of a monistic theory of sovereignty. The other thinkers listed either belong to different disciplines or have very different approaches to state and power.

Step-by-Step Solution:
Step 1: Recall that John Austin is a legal positivist who defined law as the command of the sovereign backed by sanctions. Step 2: Understand that in Austin theory, sovereignty is undivided and supreme within a political society, which matches the idea of monistic sovereignty. Step 3: Recognise that Charles Darwin is a biologist known for the theory of evolution, not for political sovereignty. Step 4: Aristotle discussed different forms of government and the concept of the polis but did not frame a modern legal doctrine of monistic sovereignty. Step 5: Karl Marx analysed class struggle and the role of the state as an instrument of class power, focusing on material and social relations rather than monistic legal sovereignty.

Verification / Alternative check:
Textbooks on political science and legal theory consistently identify John Austin as the main exponent of the monistic theory of sovereignty and legal positivism. They usually contrast his view with pluralist theories of sovereignty, which recognise multiple sources of authority in society. The names of Darwin, Aristotle, and Marx appear in entirely different contexts, confirming that Austin is the correct answer for this specific theoretical position.

Why Other Options Are Wrong:
Charles Darwin: He contributed to biology and natural science, not to formal theories of political sovereignty, so this option is clearly incorrect.

Aristotle: Although he studied politics and ethics, he did not develop a monistic legal theory of sovereignty in the sense used in modern constitutional discussions.
Karl Marx: His theory revolves around economic structures, class relations, and the eventual withering away of the state, not on an indivisible legal sovereign.

Common Pitfalls:
Students may confuse the broader idea of power or authority with the specific legal concept of sovereignty as defined by Austin. Others might associate Aristotle with all classical political ideas without distinguishing between ancient notions of rule and modern legal theories. To avoid errors, remember that monistic, legalistic sovereignty and the command theory of law are key phrases that should immediately make you think of John Austin.

Final Answer:
The thinker best known for the monistic theory of sovereignty is John Austin.