LEWISTON – Four commencement speakers representing science, history, philanthropy and college admissions brought similar messages from different viewpoints to 450 Bates College graduates Monday morning.

The speakers, all recipients of honorary degrees from the college, presented brief remarks that challenged Bates graduates to help others, to affect history, to assume leadership, and to cherish experiences and friendships.

The college’s 138th commencement exercises took place under sunny skies on the quad in front of Coram Library.

Graduates from the Twin Cities area included Paul Joseph Brunette, who received a bachelor of arts degree in political science, as well as Ryan Michael Shepard, Norway, magna cum laude, political science and rhetoric with honors in rhetoric; Jared James Cash, Norway, political science and economics; and Sarah Jean Fournier, Livermore Falls, cum laude, English.

Rita Rossi Colwell, recipient of an honorary doctor of science degree, related her memories of the assassinations of President Kennedy and others and the turmoil associated with the Vietnam War.

“You, too, have found your lives bracketed by tragedy – 9/11 and the war in Iraq,” she said. To sustained applause, she urged support for today’s men and women of the armed forces.

She told how her studies of the causes of cholera in Bangladesh led to identification of plankton in nearly every stream. She said simple boiling of water to remove the disease-causing plankton wasn’t possible because there isn’t enough firewood to burn in that impoverished country. Further studies showed that finely woven sari cloth, used in native dress, was effective as a filter.

That method has reduced the incidence of the disease there by nearly 50 percent, Dr. Colwell said.

“There are few things more gratifying in life than helping others help themselves,” she told the graduates.

David Levering Lewis, a lead historian, told the graduates he feels there have been more “assaults on economic and political democracy” in recent years than in the past 100 years. He decried materialism and “unregulated economic greed” as well as “the perverse logic of superpower omnipotence.”

Citing Winston Churchill’s observation that “Americans will always do the right thing after trying all the other alternatives,” Lewis told the graduates, “It is up to you to make history come out the right way.”

Lewis received an honorary doctor of humane letters degree.

John C. Whitehead, recipient of an honorary doctor of laws degree, spoke about the need for leadership.

“The world today cries out for leadership,” he said.

Whitehead advised the graduates, “Whatever your personality, whatever your style, think of yourself as a leader. Set your goals to make a difference in our world.”

After building a successful career in investment banking, Whitehead served in the 1980s as deputy secretary of state. For the past 20 years, Whitehead has devoted time to charitable organizations dedicated to improving people’s lives through education, international understanding, environmental preservation, and the fine and performing arts.

In 2001, he drew upon all of these commitments when he assumed the chairmanship of the Lower Manhattan Development Corporation, the agency charged with the revitalization of lower Manhattan in the wake of the World Trade Center attacks.

Milton Lambert Lindholm, Bates class of 1935, emphasized the importance of cherishing memories and friendships made at the college. He told the graduates, “You have deep roots here that need to be nourished.”

Lindholm received bachelor’s and master’s degrees from Bates in the 1930s. He was named director of admissions for men in 1944 and dean of admissions in 1960. Since his retirement in 1976, he has continued to be a spokesman for Bates. He received an honorary doctor of humane letters degree at Monday’s commencement exercises.