Joseph J. Ellis is an American historian who won the Pulitzer Prize for "Founding Brothers." He is the author of the new book "American Dialogue: The Founding Fathers and Us." The views expressed here are the author's. View more opinion on CNN.

(CNN) The Green New Deal is a bold and controversial legislative initiative proposed by the progressive wing of the Democratic Party, designed to address four pressing challenges facing American society that have thus far eluded solution.

They are: reforming our extremely expensive and inefficient health care system; reducing our currently unprecedented levels of economic inequality; rebuilding our aging infrastructure; and recovering our global leadership role to combat the existential threat posed by climate change. If we fail to address and resolve these problems, all talk of America as a "city on a hill" needs to cease.

Joseph Ellis

The great advantage of the Green New Deal initiative is that it forces and focuses a much-needed debate about the role of government in defining our agenda as a people and a nation. At present, however, critics on the right are attempting to short-circuit that debate by arguing that the Green New Deal is socialism , a loaded label with potent un-American associations for many.

Whatever you might think about the Green New Deal, it is not socialism. As Casey Stengel loved to say, you can look it up. Pick your dictionary: the Oxford English Dictionary, Merriam-Webster, Random House. They all say the same thing. Socialism is a political theory based on the principle of government ownership of the means of production; in short, the abolition of private property.

Advocates of the Green New Deal are not proposing anything of that sort. Far from being un-American, what they are proposing is a collective response to our common problems with deep roots in American history, all the way back to the American founding. The operative word then was not "socialism" but -- members of the GOP might wish to sit down to hear this -- "republicanism."

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