In her 2015 book, The Physicist and the Philosopher: Einstein, Bergson, and the Debate That Changed Our Understanding of Time, science historian Jimena Canales recounts the debate during the 1920s about whether physicists or philosophers should define the meaning time. The central event is a 1922 public debate between the young physicist Albert Einstein and the more famous philosopher Henri Bergson.
Canales presents Einstein’s position as a radical identification of physical time with what properly synchronized clocks register.
In the 1905 paper, Einstein operationalizes time through simultaneity: saying that a train arrives at 7 o’clock means that the train’s arrival and the clock hand pointing to 7 are simultaneous. Canales emphasizes that this sounds innocuous, but it effectively makes clock procedure foundational to the scientific meaning of time.
By 1922, Einstein treats this not merely as a convenient convention but as something with “objective meaning.” He insists that there are “objective events” independent of individuals and rejects alternative representations as lacking objective sense.
That is the background to his remark to Bergson: “The time of the philosophers does not exist.”
Einstein is drawing a hard boundary. There is physical time, objectively determined through clocks, light signals, and synchronization procedures, and there is psychological time, which belongs to subjective experience. What he refuses to recognize is a third category—a philosophically meaningful time that is neither merely subjective psychology nor reducible to physical measurement.
Canales’s broader point is that Einstein’s revolution did more than alter physics: it helped elevate clock time into the authoritative model of time itself. In relativity, time is operationally defined through synchronized clocks and light signals. Einstein then defended this physical time as possessing “objective meaning,” while psychological time was reduced to subjective mental construction. Hence his striking conclusion in Paris: “The time of the philosophers does not exist.”
Canales shows that Heidegger objected to exactly this move. As early as 1915, Heidegger argued that relativity concerns “the problem of measuring time, not with time itself.” In his view, Einstein had converted a measurement procedure into an ontology. Relativity assumes time to be homogeneous, quantitative, and geometrically comparable with space; but Heidegger argued that this leaves “the concept of time untouched.” Measurement freezes temporal flow into something spatial and divisible so that it can be counted.
By 1924 Heidegger sharpened the point: once time is defined as clock time, “there is no hope of ever arriving at its original meaning again.” The problem was therefore not that Einstein’s equations were experimentally wrong, but that physics had taken one specialized form of temporal representation and implicitly allowed it to stand for time as such.
Walter Benjamin pushed the problem into history and politics. Canales notes that Benjamin and Heidegger had actually studied together as young men, but Benjamin eventually developed a very different response. Benjamin attacked the idea that history simply unfolds through “homogenous, empty time.” He connected that conception directly to the modern ideology of inevitable progress: if time is an empty sequence of identical units, history appears as humanity steadily advancing along a single line.
Benjamin instead emphasized moments that are qualitatively charged—the here and now, moments in which memory, historical meaning, decision, and possibility converge. Canales ultimately places Benjamin among the thinkers who refused to reduce the significance of “now” to its coordinate on a homogeneous timeline.
An older distinction helps clarify what is at stake. Ancient Greek had more than one important temporal concept: Chronos refers to sequential, measurable time—the succession that can be counted and ordered—while Kairos means the opportune or decisive moment, the moment whose significance comes from what happens in it, not from where it falls on a clock. That Chronos/Kairos distinction is not Canales’s own organizing terminology in these passages, but it captures the philosophical fault line she traces.
So the argument can be compressed to this:
Einstein identifies objective time with what clocks can operationally measure. Heidegger replies that measuring time is not the same thing as explaining time. Benjamin shows what disappears when homogeneous clock time is projected onto history: the singular, charged moment. In older terms, modern physics became extraordinarily precise about Chronos while risking the disappearance of Kairos.
That makes Einstein’s “the time of the philosophers does not exist” much more consequential than a disagreement with Bergson. It represents a broader twentieth-century tendency to let the measurable representation of time displace the phenomenon it represents.
