Step 1: Understanding the Concept:
The question asks to identify the core idea of Rudolf von Ihering's theory of 'social utilitarianism'. Ihering was a German jurist who moved away from legal formalism and is considered a forerunner of the sociological school of jurisprudence. His central idea was about the purpose of law in society.
Step 2: Detailed Explanation:
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\item Ihering's Core Idea: Ihering viewed law as a tool to serve social purposes. He famously stated that "purpose is the creator of the entire law." He saw society as a place of constant struggle between competing individual and social interests. The purpose of law, in his view, is to reconcile these conflicting interests. The state acts as the instrument to achieve this reconciliation or balance.
\item Analyzing the Options:
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\item (A) "greatest number of people should get greatest pleasure" is the classic formulation of Bentham's utilitarianism, not Ihering's social utilitarianism.
\item (B) "based upon the social 'facts' of law" is more aligned with Eugen Ehrlich's theory of 'living law'.
\item (C) "a balance is to be struck between the competing interests in society" This perfectly captures Ihering's central thesis of law as a mechanism for reconciling conflicting interests. This is the most accurate description of his theory.
\item (D) "law is a means to social ends" is a correct statement about Ihering's philosophy but is a very general statement. Option (C) is more specific and captures the essence of \textit{how} law achieves social ends according to Ihering – by balancing interests.
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Between (C) and (D), option (C) is the more precise and complete representation of Ihering's theory of social utilitarianism, which is also known as the jurisprudence of interests.
Step 3: Final Answer:
According to Ihering's theory, a balance is to be struck between the competing interests in society.