Gaylord Nelson, co-founder of Earth Day, former state senator, governor, and U.S. senator from Wisconsin, and recipient of a 1995 Presidential Medal of Freedom for his environmental work, died on Sunday at the age of 89. His own words are a fitting epitaph:

The ultimate test of man’s conscience may be his willingness to sacrifice something today for future generations whose words of thanks will not be heard.

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Nelson passed the test with flying colors. Let’s all hope we can do the same.

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