Freedom is the great American ideal. Everybody loves freedom, and we have, in the Fourth of July, a festival that celebrates national liberation. But what, precisely, is this freedom that we all love so much?

Political theorists find it useful to distinguish between two kinds of freedom, which we call “negative” and “positive,” according an influential article written by Isaiah Berlin, the 20th-century British philosopher. Both of these ideals find expression in the Declaration of Independence.

Negative freedom means freedom from outside interference or external constraint. It is called “negative” because it is the freedom we have in the absence of restrictions. The freedom to speak your mind or to publish what you wish, without needing to get the advance permission of any public official, are classic examples of negative freedom.

So also are the natural rights asserted in the Declaration of Independence, which states that we are “endowed by our Creator with certain unalienable rights,” including the “rights to life, liberty and the pursuit of happiness.”

You might think that we’d have the most “negative” freedom in a world without government: With no laws to restrain our freedom, everyone would be free to do as they pleased.

That might be great if men were angels. In the real world, however, the absence of government always leads to the rise of thuggish gangs and brutal warlords.

Government is necessary, Thomas Jefferson wrote in the Declaration, to “secure” our natural rights. Our ancestors sought political independence from Britain, in part, because King George’s colonial governments did not particularly respect such rights.

But our Founding Fathers wanted more than to be left alone to enjoy their negative freedoms, they wanted to be in charge of their own political destiny. They didn’t just want to be free to make individual choices free from governmental restraint; they also wanted the freedom to make collective decisions about what kind of country we would become.

In short, they also wanted Berlin’s positive freedom, which they could not possess without political independence, no matter how enlightened a ruler George III might have become.

Such freedom is called “positive” because it is the freedom we have when we are able to make or accomplish something. We experience a particularly powerful form of this positive freedom when we, collectively, make the very laws we then, as individuals, follow.

The two notions of freedom can conflict with one another. One group may, collectively, embrace a law that deprives others of their basic rights, as the white citizens of the United States did when they made slavery the law of the land.

Generally, however, they are complementary. Countries that regularly hold free elections have a much better record of protecting negative freedoms than those that don’t. That is because most people value their freedom and refuse to elect leaders who don’t. Most of the exceptions, such as slavery and Jim Crow segregation in the United States, arise when a class of people are systematically excluded from political power.

In a society where there are no special privileges, where no one gets any rights that are not accorded to everyone, and where everyone has the right to vote, the voters generally use their self-governing, positive freedom to secure their fundamental, natural rights.

That is why the Declaration of Independence insists both that all are endowed with natural rights and that all are “created equal” and why Abraham Lincoln at Gettysburg said that our country was “conceived in liberty” and is “dedicated to the proposition that all men are created equal.”

What Lincoln meant was that the ideal of equal citizenship, declared in 1776, was not yet a reality, but that he, and other American patriots, were dedicated to making that ideal a reality by including more of our countrymen — and countrywomen — as equal citizens, with equal rights under the law.

Freedom today, however, seems to be under threat. We fear both that our government is infringing our negative liberties by intruding on our private lives, and we fear that our rulers are becoming so disconnected from our wishes as to make a mockery of the ideal of positive, self-governing freedom.

Freedom is always a precarious political achievement. That does not mean we can be complacent; free countries have been known to lose their freedom. To avoid that fate, we must dedicate ourselves to what Lincoln called the “great task” before his fellow citizens in 1863, to resolve that our nation shall have a “new birth of freedom.”

Joseph R. Reisert is associate professor of American constitutional law and chairman of the department of government at Colby College in Waterville.