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Alessandra Campo nous offre un compte rendu du colloque 'What is time? Einstein-Bergson 100 years later' qui a eu lieu à L'Aquila en avril dernier/Alessandra Campo reports back from the 'What is time? Einstein-Bergson 100 years later' conference which took place in L'Aquila last April Dates are anything but conventions and history, real history - write Deleuze and Guattari in A Thousand Plateaus - will never get rid of dates. When dates take on importance in individual and collective life, they work as the markers of events, and that is why they have a substantial affinity with the performativity of a password. Before reporting a fact, a date – for example April 6th, 2009 – resonates as an effective presence: something happened, an earthquake; something has passed, and the city of L'Aquila has changed forever.The noema of a date is an event and therefore, every date is a figure in which the extratemporal time of the act is welded, as such, in the fact in charge of remembering it. Similar to the photographs to which Barthes and Bazin ascribed a decisive deictic function, dates exhibit considerable performative power: the past they evoke is not empirical or historical but transcendental, absolute. Therefore, as Deleuze and Guattari  note, reactionaries hate them: dates are markers of metamorphosis and, change, as we know, is rarely accepted without opposition. “Rarely”, however, doesn’t mean “never” and in L'Aquila, on April 6th, 2019, something has changed. Philosophers and scientists from all over the world returned to confront one another, under the sign of philia and sophia, on a theme that has long divided them: the nature of time. These discussions were conducted under the sign of mutual understanding: : everyone in attendance was willing to make sure their personal philosophical inclinations did not get in the way of the exchange of different, sometimes opposing points of view thus making room for truly novel ideas.On April 6th, 1922, Einstein and Bergson met and clashed in Paris. Marco Bersanelli, in his cosmological talk that closed the conference, clarified the meaning of the change of perspective that resulted from their debate. Contrary to what Einstein claimed, the time the philosopher deals with is nothing other than the one on which the physicist reflects: the cosmic microwave oven mapped by the Plank satellite, in reality, is nothing else than that unique time that Bergson laid as the foundation of the plurality of individual times almost a hundred years ago. There were only two times for Einstein: the time of consciousness and the time of science. There was no room for a third, philosophical, time. Psychological time concerns the simultaneity of perceptions; physical time, the simultaneity of events. But only the latter, Einstein wrote to Besso in 1924, is truly absolute, in that it is independent from the observer. Bergson, in his opinion, was guilty of not grasping this point and of thinking relativity exclusively in the terms suggested by the difference of the two clocks.                 And yet, as Jimena Canales has argued, despite resorting to other arguments, Bergson also defended the absolute character of simultaneity. For Bergson, simultaneity is absolute to the extent that it disregards the physical adjustment of the clocks. It is absolute, in other words, because it is not reducible to the synchrony between two measurements. Instead of measurement being derived from simultaneity, wrote Bergson in Duration and Simultaneity, simultaneity presupposes measurement and that is why, one cannot set a time without placing the consciousness that experiences it. Every measurement implies consciousness as its own transcendental foundation.                And yet, as Jimena Canales has argued, despite resorting to other arguments, Bergson also defended the absolute character of simultaneity. For Bergson, simultaneity is absolute to the extent that it disregards the physical adjustment of the clocks. It is absolute, in other words, because it is not reducible to the synchrony between two measurements. Instead of measurement being derived from simultaneity, wrote Bergson in Duration and Simultaneity, simultaneity presupposes measurement and that is why, one cannot set a time without placing the consciousness that experiences it. Every measurement implies consciousness as its own transcendental foundation. Einstein did not agree. According to him, scientists must go beyond consciousness and experience to correctly measure nature. The clock on which we must rely is in this sense ideal: mathematical and not biological. The psychological quest of simultaneity is in fact always inaccurate. And yet, Bergson later remarked, to establish to what extent it is inaccurate, through calculations or laboratory experiments, it is still necessary to resort to (imprecise) psychological findings of simultaneity.  Marc Wittmann, Mauro Dorato and Pierre Montebello’s talks were dedicated, in various ways, to this co-implication of psychological and physical time, of everyday experience and scientific results.  Even Etienne Klein and Yuval Dolev (albeit with some differences), have insisted on reiterating the impossibility of grasping the latter without considering the former and vice versa (although,  they argued, this may generate more problems than solutions). The guiding principle of these talks, in other words, was akin to the principle Alfred North Whitehead started formulating in the 1920s: nature is one, it is not bifurcated. Matthew T. Segall and Michel Weber restored in their talks the importance this English philosopher and mathematician’s work, by emphasizing the mediating role of his thinking with respect to the positions of Bergson and Einstein. Segall in particular, after a comparing Whitehead's relational ontology and Bergson's metaphysics of duration, showed the Whitehedian implications of Carlo Rovelli's version of quantum gravity. Weber, on the other hand, analysed the “creative advance into novelty,” which assumes that (1) genuine novelty appears in the World, (2) past events do not completely vanish, their ontological status is changed, memorized, so to speak, and (3) there is an upward trend in terms of “intensity” or “value” of experience.                 Julian Barbour is perhaps the speaker who distanced himself the most from the idea of a creative advance into novelty, even though he did not entirely distance himself from that of the arrow of time (which - he told us - is not just one). In L'Aquila he presented the results of his latest work on the dynamics of shapes ("shape is all I need - he said – to develop a new definition of instant”). These results that he himself summarized in the formula "nouns come before verbs", go against the Bergsonian and Whiteheadian spirit, . Carl Hoefer, preceded him with a wonderful talk intelligently presenting, the limits and the argumentative errors both of theories in favour and against a block universe.Since 1908, it has been common to suppose that the structure of spacetime revealed through modern physical theories leaves no room for absolute simultaneity, which seems to be a prerequisite for a genuine passage of time. But there have been many dissenters (in addition to Bergson) who have maintained that physics has by no means – so far, at least – demonstrated that there is no genuine passage of time in our world.  But, since the reasons supporting both the former and the latter position are weak, Hoefer concluded, the debate is still open.  Rocco Ronchi reframed the debate, working above all on a reinterpretation of Duration and Simultaneity. He argued that we should think about the relationship between the time of physics and the time of nature like Bergson thought the relation between the possible and the real. And it is only if we do so, according to Ronchi, that the twin paradox ceases to be a paradox: Paul is not real, he is only a vision of Peter. But Peter isn’t real either, he is only an arbitrarily assumed reference system, indispensable for configuring the universe. Indeed, what is real, even more real than Peter and Paul, is the interval that separates them.                 After Relativity, the interval is no longer space, but time, and, more precisely, the creative duration of unpredictable novelties. But what kind of time is time reduced to a gap? Elie During focused on the notion of coexistence to think about the duration of durations, as the duration of simultaneities. In fact, if Bergson advocates anything, it is the formal unity of the concept of time as the medium of both change and coexistence. And, this formal unity essentially involves some measure of extended simultaneity beyond the varieties of local time. Duration without simultaneity has nothing specifically temporal about it. But the same goes for the reverse. Giuseppe Longo, biologist and mathematician who has been studying those “living clocks” that are organisms for a long time, argued that simultaneity without duration has nothing specifically temporal about it. Longo proposed an abstract mathematical framework for describing some proper features of biological time, elaborating on the peculiar irreversibility of phylogenetic and ontogenetic time(s) which may require an extra observable time in the same dimension, or even an extra dimension for a better understanding of the role of changing spaces of possibilities (phase spaces) and of rare events in biological evolution. The connection between time irreversibility, symmetry breaking and randomness in various theoretical frames was also suggested by Guido Tonelli and Eugenio Coccia. Coccia analyzed gravity’s effect on time (gravity deforms time and this give rise to some paradoxical situations, for instance black holes, the extreme fruits of gravity) while Tonelli, who works at CERN in Geneva, asked what the time lived by elementary constituents of matter is. Tonelli, in particular, illustrated the phenomena that occur when exploring the smallest space-time dimensions and, and discussed the strange relationship between time and energy that transforms the void into a field of matter. He explained how particles can be accelerated to the speed of light. But which phenomena are created in this state? And how do you see how much a quark lives? What tricks are used to measure time intervals that are too small to be measured? Finally, how long does a Higgs boson live?  Relativity theories only tell half of the story of modern physics’ challenges to the passage of time: quantum theories bring new challenges with them, but also new opportunities for defending passage. Many approaches – as Christian Wüthrich argued in his talk - suggest that space and time will not be part of the fundamental furniture of the world, adumbrating the most radical revolution in our understanding of time yet. Instead of being fundamental, space and time are emergent properties of the fundamentally non-spatiotemporal structures postulated by quantum gravity, very much like the solidity of a glass and the liquidity of the water it contains Spacetime – he argued - is a “regional” option. Apart from the well-behaved spatiotemporal 'phase' we inhabit, our universe contains a very “early epoch”, which should not be expected to be spatiotemporal -- the big bang. Quantum gravity suggests that “at” or “near” the big bang, we find a non-spatiotemporal “phase”. If this is right, then it would suggest another way in which time might emerge: as a “transition” from an “earlier” non-spatiotemporal to a “later” spatiotemporal states of the universe. How should we categorize the emergence of spacetime - or failure thereof - in these contexts? How can we conceive of a “transition” from timelessness to the regular temporal evolution of our world? From Plato through Leibniz to Russell, metaphysics was crudely dualist. In the vocabulary of Nicolaï Hartmann cited by Jean-Claude Dumoncel, “Being” is divided in the Sosein of the universals fx and the Dasein of the particulars a. But symbolic logic was made by mathematicians, and in mathematics the typical a is a number, again in the Sosein. Inversely, the Sosein is supposed to include the “caballeity”. Darwin changed all this. In order for caballeity to sit in the Sosein, the ancestors of the horse and the horses must previously pop in the Dasein. In Whitehead’s view, the only “eternal objects” are geometrical forms, and colours. Therefore, the Zeitsein may be defined as the union of the Dasein and of the quiddities which, in the Sosein, are derived from the evolution at work in the Dasein Dumoncel argued that since temporal logic is a kind of modal logic, the contribution of logic to the question “What is time?” must be asked to the part of temporal logic where the modal involvement (in Quine’s sense) reaches its maximum, that is in “tense logic”. If time is indisputably a feature of nature, the word becoming, as this was noticed by Broad, reminds us that it is primarily a feature of being. And this is what must be described in the concept of Zeitsein: a being that is the timeless event of time and which, as such, has a date: 6 April 2019. A date to remember and not to forget, because if man says “time passes”, time says “man passes”.  Thus at least recites, in the absolute past, an Indian adage.