Philosophy
The Nature of Necessity and the Essentialism Debate
Quick fact
The essentialist debate over necessity was famously shaped by Saul Kripke, who argued that 'Water is H2O' is a necessary truth discovered by science, not a truth of logic—a claim that challenges the old idea that all necessary truths are known a priori.
Why this is interesting
You know that 2+2=4 and that water is H2O. But why are these truths not just true, but necessarily true—and what makes them so?