Why did Socrates believe that someone who truly knows what is right will act rightly?

Socrates believed that virtue is a form of knowledge, a doctrine often summarized by the idea that to know the good is to do the good.123

His reasoning was rooted in the conviction that reason, when properly cultivated, should be the all-controlling factor in human life. Socrates argued that if an individual truly understands what is right, their emotions and desires will naturally align with that belief. Consequently, he denied the possibility of "weakness of will"—the notion that someone could knowingly act in a way they believe to be wrong.2

From this perspective, any failure to act virtuously is not a result of choosing evil, but rather a failure of understanding; the person simply misidentifies what virtue actually is. Because he viewed the cultivation of virtue as the most important human obligation, he dedicated his life to seeking precise definitions of ethical concepts, believing that if we could discover the true nature of virtues like courage or justice, we would possess everything necessary to live well.23