EASTON, Pa.—U.S. Vice President Joe Biden used a speech at Lafayette College on Wednesday evening to urge Americans to discount President Obama's opponents and get behind the administration's vision for the economy.

Biden said achieving Obama's goals in education, health care, infrastructure and renewable energy are the key to economic growth and America's place on the world stage. He repeatedly referred to "naysayers" who question the administration's goals, although he didn't name Republican leaders or presumptive GOP presidential nominee Mitt Romney.

"You have to ask yourself the question, not only what if we do, but what if we don't?" Biden said. "I ask you, where will those middle-class jobs in the 21st century come from if not from entire new industries?"

Biden outlined some of Obama's goals for the coming years, such as treating Alzheimer's effectively, generating 80 percent of electricity from clean sources, giving 80 percent of Americans access to high-speed rail and having the highest percentage of college graduates in the world.

Biden noted past presidents set goals to build the intercontinental railroad, bring electricity to all parts of the country and fly to the moon. He said no single company or group of companies was willing to make those investments, and it took presidential leadership and government investment to jump-start those projects.

Some of the president's opponents don't understand that part of the country's past, Biden said, and naysayers to similar initiatives have been proven wrong throughout American history.

"We will either lead in the 21st century or we will follow," Biden said. "There is no standing still. That is the choice before us."

Biden said those investments in renewable energy, infrastructure, health care and education will create good-paying jobs for the future and drive the economy, noting there are only so many jobs on Wall Street.

"I love these guys who tell us we are engaged in class warfare, class envy," Biden said. "There's no path other than through the middle class. When the middle class does well the poor have a chance and the wealthy do better."

A spokeswoman for the Republican National Committee wrote in a statement released after the speech that the administration's economic vision has failed investments and left Americans struggling to find work.

"Their big spending agenda has led to trillion dollar deficits, crushing debt and an American economy this is less competitive," Allie Brandenburger said.

Biden was on campus to deliver the school's "Lives of Liberty" lecture.