Einstein thanks Hume for help with relativity

In 1915, Albert Einstein wrote to Moritz Schlick praising "Hume, whose Treatise of Human Nature I had studied avidly and with admiration shortly before discovering the theory of relativity. It is very possible that without these philosophical studies I would not have arrived at the solution."

Decades later, Einstein would reiterate that "In so far as I can be aware, the immediate influence of D. Hume on me was great. I read him with Konrad Habicht and Solovine in Bern" And 1949, Einstein would write that Hume helped him reject the "axiom of the absolute character of time, viz, simultaneity". Einstein continues, "The type of critical reasoning required for the discovery of this central point... was decisively furthered, in my case, especially by the reading of David Hume’s and Ernst Mach’s philosophical writings."

According to John Norton and Matias Slavov, Hume's empiricist account of concepts was the important thing Einstein found in the Treatise. If time is an a priori form of sensibility with absolute simultaneity built in, as Kant suggested in replying to Hume, relativistic time dilation is impossible. But if the concept of time is empirically acquired and conventionally codified, absolute simultaneity can be a mere approximation suitable for slow things, which fails closer to the speed of light.

The picture is of the mathematician Conrad Habicht, the philosopher Maurice Solovine, and Einstein. They formed a little philosophy reading group in Switzerland and read Hume's Treatise as well as works by Mill, Poincare, and Spinoza. At one point Solovine missed a meeting that was held in his apartment to attend a concert. Einstein and Habicht trashed the apartment, taunted Solovine, and made sure the next meeting lasted until morning to make up for lost time. They remained friends for the rest of their lives.

Well over a century after Hume remarked that his Treatise "fell dead-born from the press", Einstein used it to discover the nature of space and time, and the shape of the universe. It gives me optimism for the power of empiricist philosophy. Many great mysteries may remain to be solved by those carrying empirical data in one hand and Hume's Treatise in the other.