Why did Hilary Putnam defend realism throughout his philosophical career?

Hilary Putnam defended realism throughout his career because he believed it was essential to avoid the pitfalls of subjectivism and relativism, which he viewed as forms of radical skepticism that are fundamentally flawed.1

While he rejected "metaphysical realism"—the idea that we can describe a mind-independent world through a direct correspondence between language and entities—he maintained a "commonsense realism." He argued that objective truth is necessary and that "truth under a description" is sufficient to account for the success of science and mathematics.1

Putnam’s commitment to realism was driven by several key convictions:
* Anti-Skepticism: He argued that skeptical scenarios, such as the "brain in a vat" thought experiment, are self-defeating and paradoxical because they rely on a theory of meaning that renders the skeptic's own claims false.1
* Indispensability: In the philosophy of mathematics, he and W.V.O. Quine argued that because mathematical objects are indispensable to our best scientific theories, their reality must be accepted.1
* Scientific Integrity: He sought to reconcile realism with complex fields like quantum mechanics, insisting that theories represent real physical states rather than mere algorithms for calculation.1