(This op-ed originally appeared in the February 24, 2011, issue of The Chronicle of Philanthropy.)

Great philanthropy is distinguished not by the sheer size of a gift or grant but by what it accomplishes.

Giving money away—writing checks, making payout requirements—is relatively simple; using money to produce real results for society is agonizingly hard.

A commitment to pursue results is a choice to wrestle with fundamental questions like “What is success and how will it be achieved?,” “What am I accountable for?,” and the most essential question of all: “What are my values and beliefs?”

That last question is deeply relevant for donors, their families, and even their foundation executives.

In making philanthropic decisions, the heart is always connected to the head.

Thus almost every philanthropic effort contains a huge dose of “me,” driven by the values and passions of the donor, perhaps shaped by family members and trustees, and further interpreted by foundation leaders.

When donors are clear about their beliefs and concentrate their giving in areas of deep personal interest, they are most likely to mobilize and motivate others to ask the tough questions that lead to results.

Philanthropy comes in a variety of forms, with a world of possibilities from which to choose. This absolute freedom may be philanthropy’s great strength, allowing donors to express their individuality and creating room for innovation across a world of possibilities.

But when a donor’s efforts are not anchored in explicit personal beliefs, that freedom can become an Achilles’ heel.

Ambiguity about one’s values and beliefs is the enemy of impact. It will waste resources, confuse strategic decisions, and muddle implementation.

Ambiguity will also confound family members, trustees, and foundation leaders working to support the donor’s intentions.

The more one leaves values and beliefs open to interpretation, the more others will fill that gap by inserting their own personal perspectives. This pattern is evident across foundations in which new chief executives and program officers routinely alter priorities and shift strategies based on what they think is right, all within the context of “donor intent.”

The early history of the John D. and Catherine T. MacArthur Foundation, one of the largest in the United States, provides a cautionary example of what can happen when a donor isn’t explicit about his or her values and beliefs.

When John MacArthur set up the foundation in 1978, he purposely gave its small board no instruction about how the foundation should be organized or what it should do.

“I know of a number of foundations where the donors tried to run them from their graves,” he explained. “I have guaranteed the trustees that when I am gone, they can run the show.”

Mr. MacArthur died just as his foundation was beginning its work, and the trustees did indeed run the show, though not in the ways he might have imagined.

Almost immediately, a dispute erupted over its direction. On one side were Mr. MacArthur’s former associates, self-described “Midwestern businessmen devoted to free enterprise and opposed to more government controls”; on the other, Mr. MacArthur’s son, Roderick, who “declared that foundations had to be on the cutting edge of social change,” according to The Golden Donors, a philanthropy history by Waldemar A. Nielsen.

The following year, the board enlarged itself to 15 members to help resolve the disputes. Although individual trustees initiated some excellent programs, including the MacArthur Fellows Program, the wrangling continued.

Roderick’s death at the end of 1984 quieted the tumult, but it would take another 15 years before problems with the foundation’s direction were entirely resolved.

Ambiguity may lead to open conflict, as with the MacArthur foundation. More often, philanthropic decision makers split the difference, creating a potpourri of values that blends multiple perspectives and agendas.

A typical manifestation of this phenomenon is that money is spread over more and more recipients, which makes it tough to stay strategically focused.

The foundation leaders may feel good about what they are doing, but that does not mean they’re actually doing good.

Clarifying values and beliefs allows one to give intelligently and deliver results. Look at what John V.N. Dorr and his wife, Nell, accomplished.

Mr. Dorr, a metallurgist, chemical engineer and protégé of Thomas Edison, founded an engineering firm that made him wealthy enough to establish the Dorr Foundation in 1940.

The foundation initially financed a wide range of small projects.

Then Nell Dorr pointed out that after dark, especially in bad weather, headlight glare from oncoming traffic made drivers either hug the center line of the highway or swerve away from that line onto the soft shoulder of the road—sometimes with tragic consequences.

Thinking about the problem, Mr. Dorr became convinced that painting a white stripe on the far right side of the road to demarcate the outside edge of the pavement would not only minimize the threat to drivers but also make pedestrians safer. In a test of the stripes on New York’s Hutchinson River Parkway in the 1950s, accidents and injuries dropped 55 percent over seven months.

Because the Dorrs were committed to learning what works for a cause they cared about, they invested both their money and their time over multiple years to achieve the results they desired.

By the early 1960s, as a result of the foundation’s focus and investment and Mr. Dorr’s relentless lobbying, the highway shoulder line had gained near-universal acceptance. An increasingly mobile population became a lot safer, and many thousands of lives were saved.

Pierre Omidyar, the founder of eBay, and his wife, Pam, offer a more contemporary illustration of translating values into action.

They believe deeply in the power of the individual to drive change, especially when enabled by technology. Hence their active support for Ushahidi, a Web platform that gathers data from individual e-mails and text messages and represents them in a visual format (such as a map or timeline) that can inform people and galvanize them to act.

First used to chart post-election violence in Kenya, the Ushahidi platform has been used by citizens and organizations around the world to publicize—and spark—real-time responses to events like the earthquake in Haiti, the Israeli invasion of Gaza, and the BP explosion in the Gulf of Mexico.

Though generations apart, what is similar about these donors is that clarity about their values and beliefs determined how they decided to use their philanthropic resources to make very specific differences in the world.

This may sound like the most common of common denominators.

After all, you would be hard-pressed to find a philanthropist who doesn’t hope to make a difference, let alone one who would knowingly set out to waste hard-earned money.

But aspiring to do “good” isn’t enough. Effective philanthropy is fundamentally personal. Philanthropists accomplish far more when they pursue results driven explicitly by who they are and what they care about most.