So part of my summer reading list is the Oliver Wendell Holmes--Harold Laski Letters (abridged by Alger Hiss!!), which offer an interesting and not always conventional window into Progressive thought. Laski is mildly surprising in places, such as his comment that "I think on the whole that it really is doubtful, once you regard liberty as a process and not an emotion, whether Rousseau didn't do more harm than good."
But I especially like this joke from Holmes: "Two old friends meet--'What are you doing now?' 'I'm in the legislature, but don't tell my dear old mother. She thinks I'm a bartender.'"