In All the Light We Cannot See, the relationship between scientific objectivity and the ability to empathize emerge as a motif. Werner is the central character who engages with this motif, grappling with the coldness and calculation of German scientific institutions in the face of his own, deeply personal, deeply human connection to the machines that spark his curiosity. His love for machines and physics and nature stems from the profound ability to empathize—to view even non-living components of the universe as an extension of himself. Werner's love of science comes from an appreciation of beauty and life.
Werner struggles with his empathy as he finds himself entrenched in the German war machine, presented with an alternative version of science based in Enlightenment ideals of "objectivity." The Professor and Herr Siedler, among others, push forth a narrative of science as a tool of empire, meant to extract capital from people and "value" from the earth around them. When Werner is asked to weaponize his scientific curiosity for the sake of Nazi Germany—as many famous German scientists were—he struggles, his values clashing with those of Nazi scientific institutions. In the context of these institutions, his ability to empathize is viewed as detrimental, an obstacle to any "true objectivity" he might achieve. Ironically, this apparently valuable "objectivity" leads to the cold-blooded murder and genocide of millions of people.
Throughout All the Light We Cannot See, Doerr's characters ponder a motif of selfishness, wondering whether or not empathy for others can persist within the violent setting of war. In Section One, for instance, Herr Siedler remarks on history, narrative, and self-interest, speaking to Werner as the young boy fixes Siedler's radio set:
You know the greatest lesson of history? It’s that history is whatever the victors say it is. That’s
the lesson. Whoever wins, that’s who decides the history. We act in our own self-interest. Of
course we do. Name me a person or a nation who does not. The trick is figuring out where your
interests are.
Herr Siedler appears to believe that individuals act only in their own self-interest—that the individual, above all else, is the principal unit of "civilization," as opposed to the community. Siedler posits this concept as a given: "of course" people are selfish, for there is nothing else a person can be. Werner grapples with this ideology, eventually proving Herr Siedler wrong himself by forfeiting his life to save Marie-Laure. She is a stranger to him, and Werner gains nothing appreciable by helping her—but he is not acting out of self-interest. He saves Marie-Laure out of kindness, out of love for humanity, and out of simple human kinship.