c) William James

William James is renowned for popularizing Pragmatism, a philosophy that greatly influenced thought during the Progressive Era. Pragmatism, rooted in the idea that the truth of an idea is measured by its practical consequences, resonated with the era’s focus on reform and action. James’ approach emphasized the adaptability of thought and the application of practical solutions to social issues. His philosophical contributions inspired many Progressive thinkers and reformers, aligning with the era’s emphasis on empirical evidence, experimentation, and the betterment of society. William James’ Pragmatism thus played a pivotal role in shaping the intellectual landscape of the Progressive Era in the United States.