How did Sophist ideas encourage later Greek philosophers to investigate ethics more deeply?

The Sophists played a crucial, albeit ironic, role in stimulating the development of Western moral philosophy by challenging traditional Greek values and prompting later thinkers to investigate ethics more rigorously.1

Their influence encouraged deeper philosophical inquiry in several key ways:

• Challenging Tradition: By questioning whether moral codes were objective facts of nature or merely social conventions, Sophists like Protagoras and Thrasymachus forced philosophers to move beyond unreflecting faith and tradition. This shift required defenders of morality to provide reasoned arguments rather than simple appeals to custom.12
• Focus on Human Nature: The Sophists shifted the philosophical focus from the physical world to human society and human nature. By treating human nature as a potential source for norms of conduct, they established an approach that Plato and Aristotle later adopted and refined in their own ethical systems.34
• Reaction to Skepticism: The radical positions held by some Sophists—such as ethical relativism or the idea that "might makes right"—created an intellectual impasse. This provoked Socrates, Plato, and Aristotle to probe more deeply into ethics to determine if these potentially destructive conclusions could be resisted, ultimately building the foundation of Western moral philosophy.31

The serious, rational discussion of these moral problems by the Sophists helped transform ethics into a subject of systematic inquiry, proving that moral theory could be analyzed and taught.35