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.

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

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