The term “progressivism” is used widely across the political spectrum when people refer to the left. It means a consistent, zealous belief in certain kinds of social change to be driven by government action.
“Progress” sounds nonpolitical and is sometimes meant that way. But the desire for progress becomes very political indeed when it turns into an “ism,” and “progress” is considered the foremost responsibility of government.
This is what happens when progress’s zealots demote, often virtually ignore, every value that competes with it. “Progress” becomes an ideology, an “ism.”
Thus, “progressivism,” is a predominantly leftist ideology as it is wedded to the notions that human nature is malleable and that limitations on the actions of government to change people’s behavior in desired ways are impediments to “progress.”
The left most wants progress in two areas: a reduction of pain and difficulty in life, and the most complete equality possible—not in terms of legal treatment, but in terms of resources and power, what is often called “equality of result,” or “equity.” In pure progressivism, these concerns or values tend to outrank everything.
Throughout most of William Rusher’s career in the latter half of the 20th century, progressives were usually called “liberals.” Most were less extreme than today’s progressives, but their ideology was in essence the same. “Liberals,” “liberal,” and “liberalism” are the terms you will generally find Rusher using on this website. His contemporaries, right and left, tended to use it as well. But “liberals” can also be thought of as progressives, and “liberalism” as progressivism.