Alia E. Dastagir

USA TODAY

When you place your hand over your heart during the pledge of allegiance, the national anthem or the sight of a rising American flag, what do you feel?

You want to. You have to. Perhaps you feel nothing at all.

San Francisco 49ers quarterback Colin Kaepernick feels something. His refusal to stand during the national anthem before games has reinvigorated a debate — and aroused a great deal of acrimony — about what it means to be a patriot in America.

It's a question with a mutable answer, one that changes depending on our place in history's arc, as well as where one falls on the political divide. Kaepernick, his supporters and the athletes who have joined his protest against racial injustice and police brutality, say his actions show he loves America and wants to better it. Critics say he is disrespecting his country and especially the military, the most vociferous detractors using racial epithets and suggesting he make another nation his home.

Kaepernick refused to stand for the national anthem before a preseason game against the Green Bay Packers in August. He has continued to either sit or kneel in games since and said he will stop his silent protest when he feels it is appropriate.

Soccer star Megan Rapinoe follows Colin Kaepernick in kneeling for anthem

The controversy affirms that while we agree patriotism means love for and pride in one's nation, we are perpetually ensnared in an often vicious debate about what a patriot looks like, how a patriot acts and what a patriot should do if he or she feels the country is moving in the wrong direction.

"Patriotism is completely subjective," said Leonie Huddy, a professor of political science at the State University of New York-Stony Brook and co-author of the study American Patriotism, National Identity, and Political Involvement.

A conservative who considers himself or herself a patriot may find the American flag sacrosanct, while a liberal could burn that same flag to protest a war and maintain they love their country no less.

Santa Clara police might not work 49ers games amid Colin Kaepernick protest

This debate over national loyalty is as old as the nation itself.

After the American revolution, we became citizens of a nation rather than subjects of a crown, but it wasn't until the beginning of the 19th century that people started to see themselves more and more as Americans.

"The notion of the American nation was resolved by the Civil War," said Alan Singer, a social studies educator at Hofstra University in New York. "And the notion of primary loyalty toward the United States was something that resolved over time."

Military personnel voice their support for Colin Kaepernick on Twitter

In some ways, patriotism helped us make sense of a new world. And dissent was always a part of it.

Abolitionist William Lloyd Garrison thought the Constitution was "an agreement with Hell." Henry David Thoreau refused to pay taxes that supported slavery. As a congressman, Abraham Lincoln challenged President Polk by vehemently opposing the Mexican-American War.

There are times, especially during war, when dissent is less tolerated, when our freedoms feel more fragile. During World War I, opponents of the war were jailed. During the Cold War, all dissent was seen as suspect. One could argue that post-9/11, we are always at war.

"Since 9/11 the idea of dissent has been seen as un-American," Singer said. Terrorism replaced communism as a global enemy, and Americans are told the threat of terrorism is omnipresent.

Roger Goodell on Colin Kaepernick: 'We believe very strongly in patriotism in the NFL'

Kaepernick has joined a group of athletes who have pushed for social change, including John Carlos and Tommie Smith, Muhammad Ali, Jackie Robinson, Bill Russell, Kareem Abdul-Jabbar, Jim Brown, Arthur Ashe and Billie Jean King, among others.

"I'm not anti-American. I love America," Kaepernick said after the 49ers' preseason victory over San Diego last week. "I love people. That's why I'm doing this. I want to help make America better, and I think having these conversations helps everybody have a better understanding of where everybody is coming from."

It's no surprise the controversy is also playing out on the political stage. Republican presidential nominee Donald Trump suggested Kaepernick's discontent means America isn’t the right place for the athlete. President Obama said the quarterback is exercising his constitutional right. Democratic presidential candidate Hillary Clinton hasn't joined the fray.

The debate is part of a broader political conversation the nation is having this presidential election about what it means to love and protect the country. Daniel Druckman, a political psychologist and professor at George Mason University in Virginia, said it evinces an important distinction between patriotism and nationalism.

Patriotism is love for country without corresponding hate for others. Nationalism requires you have an enemy to reaffirm that loyalty. Trump's negative rhetoric toward Muslim and Mexican immigrants, Druckman said, echoes the latter.

Kaepernick isn't breaking the law, though to many, even to those who support his right to protest, he is defying something sacred (the ritual of the national anthem) in a place that feels sacred (the sports arena).

Colin Kaepernick says he'll donate his proceeds from his soaring jersey sales to charity

"We are trained as children to internalize rules like saying the pledge of allegiance or singing the national anthem," Huddy said. "We have a very emotional and visceral reaction to Kaepernick. It turns the stomach, because it violates something we are trained to respect."

Druckman's research suggests people need patriotism. We may not be born requiring it, but we grow to desire it. It helps us gain a sense of identity and self-esteem. It helps us belong.

"The need for patriotism is universal," he said. "The expression is not."

Being a patriot means when the first notes of the national anthem reach your ears, you place your hand over your heart. And, in America, sometimes it means you kneel.

Dastagir is a mobile editor who writes about media and culture.