Final answer:
The essence of the quote is most closely aligned with Socrates' belief that the state of one's soul or character is of utmost importance and that living without virtue is akin to being dead inside.
Step-by-step explanation:
The quote “The worst thing that can happen to a man is to live but die inside” is not directly attributable to any of the listed philosophers as it does not match precisely any well-known quotations from their writings. However, this sentiment aligns most closely with Socrates who, in various texts attributed to him, emphasizes the importance of the state of one's soul or character over physical life. Socrates, as recounted in Plato's works, believed that harm to one's character was a greater misfortune than physical harm, and the notion that one can be alive yet dead inside resonates with his views on the significance of living a virtuous and examined life.
Thus, in the context of the given options, it would be reasonable to associate the spirit of this quote with the philosophy of Socrates. Socrates valued the state of the soul and ethical living, suggesting that the unexamined life is not worth living, and he regarded making choices that lead to harm as a form of self-corruption. Socrates' trial and ultimate execution, as detailed in Plato's “Apology”, further illustrate his commitment to these principles, preferring to die rather than compromise his moral integrity. This steadfast dedication to virtue over physical life echoes the concept of living but dying inside when one's values and character are compromised.