In this letter to the British philosopher, public intellectual, and anti-war activist Bertrand Russell, Muller stresses that he does not just want to sign on blindly to his peace initiative. Instead, he wants it made clear that he would not approve of America disarming without a similar commitment from the USSR.

Muller tried to launch the Foundation for Germinal Choice to facilitate humanity taking control of its own reproductive destiny. Ultimately it had little success and put Muller in uncomfortable political company. This circular letter was used to garner support.

Muller increasingly became a public voice for science, above all arguing for a scientific rationalism, which held that science needed to be safe from interference and censorship, and its results and implications not willfully ignored. This entailed staunch criticism of Lysenkoism. But in his home country, it also meant striking a careful balance between advocating for free and open discourse, and not being too tolerant of intolerant ideologies--among which he now included communism. Scarred by his time in the Soviet Union and the brutality of Stalin, as well as the continued international communist support of Lysenkoism, Muller had little sympathy left for the communist party. He was similarly distrustful of the Soviet Union in international politics, and while he was anti-war and often joined in anti-war causes with other eminent scientists, he thought disarmament without a concordant agreement from the USSR would be a mistake. He signed the 1955 Einstein - Russell Manifesto authored by Albert Einstein and Bertrand Russell that warned of the dangers of atomic weapons, but with qualifications. From 1956 to 1958 he served as president of the American Humanist Association, continuing to push his compassionate scientific rationalism. Muller was elected Humanist of the Year in 1963. Deeply entwined with his humanism, he also invested time in promoting germinal choice (sperm banking) as a way for humanity to have more control over reproduction.

In this letter to fellow IU geneticist Irwin Herskowitz, Muller recounts his experiences teaching James Watson. Watson later singled-out Muller as an important influence on his thinking, and honored Muller’s legacy with a conference devoted to him in 2015. Watson did his PhD under Salvador Luria, but with Muller's encouragement and blessing.

This copy of a test from Muller's Zoology 344 class gives some insight into him as a teacher. A different class of his, "Mutation and the Gene," was especially legendary. Muller had been on the frontline of many of the major discoveries of 20th century genetics and could provide a first person perspective.

Despite Muller’s rising status as an international public scientist and humanist from his Nobel Prize onward, in the trenches of genetics, classical genetics and Drosophila studies were losing pride of place. Beginning in the 1940s, new model organisms, like the fungus Neurospora, bacteria, and bacteriophages (viruses that infect bacteria), were becoming of increasing interest. The discovery of the structure of DNA in 1953 led to new excitement about studying the raw material of heredity directly, rather than mediated through breeding experiments. Despite the shift away from fly genetics, Muller was no member of the old guard. He had long been advocating for the integration of physics, chemistry, and genetics which heralded the new era of molecular genetics and encouraged the department to move in that direction. One of the discoverers of DNA, James Watson, specifically went to IU in 1947 because of Muller, where he took Muller’s advanced genetics course.

Another famous student of Muller's was the astronomer and science popularizer Carl Sagan, best known for the book and documentary Cosmos. Muller was one of his scientific heroes. Sagan shared Muller's interests in science fiction and extra-terrestrial life, and inherited Muller's thoughts on public science and the dangers of nuclear weapons. This is a picture of Mars sent to the Mullers by Sagan in 1955.

Muller’s work on the gene as the basis of life was the intellectual ancestor of the new exuberance about DNA, though not every molecular geneticist was aware of the full extent of this heritage.