'Ich lerne sehen. Ich weiß nicht, woran es liegt, es geht alles tiefer in mich ein und bleibt nicht an der Stelle stehen, wo es sonst immer zu Ende war. Ich habe ein Inneres, von dem ich nicht wußte. Alles geht jetzt dorthin. Ich weiß nicht, was dort geschieht.'

'Porquoi est-ce si difficile ? C'est déjà une question de sémiotique perceptive. Pas facile de percevoir les choses par le milieu, et non de haut en bas ou inversement, de gauche à droite ou inversement : essayez et vous verrez que tout change. Ce n'est pas facile de voir l'herbe dans les choses et les mots…'

'What, then, is sensibility? In its most basic and essential determination, from which all other determinations must flow, sensibility is simply the possibility anything possesses to suffer an event where it is taken outside itself, and involuntarily so, where its identity is exceeded by something not in its control. As Diderot says in his Encyclopédie entry on sensation: "Les sensations font sortir l'ame hors d'elle meme." Or, as he says in another context, listing specific cases of events associated with sensibility that mark instances of a self losing itself and its identity: "Sensibility, according to the only accepted usage of that word up until now, is, it seems to me, that disposition in beings, always accompanied by a weakness of the organs—a consequence of excessive mobility of the diaphragm, liveliness of the imagination, or irritability of nerves—that causes them to sympathize, to shudder, to admire, to fear, to be disturbed, to weep to faint, to help others, to run away, to cry out, to lose their reason, to exaggerate, to despise, to disdain, to have no precise idea whatever of the truth, goodness, or beauty, to run mad." Sensibility thus marks both an outside and a possible experience of madness. The outside in question here is, again, not a simple externality, but, as in the case of the conversation, something internal to the soul, part of its very constitution: the soul as ex-posed or ecstatic, "containing" as what is most internal to it, a fundamental ex-cess. Diderot names this excess madness, the madness of the outside.

In the case mentioned above the vocabulary of sensibility and sensation, and the madness of the outside implied by it, is used in relation to the human realm. But this vocabulary is not limited to this realm, and marks for Diderot the basic "determination" of anything that is. Anything whatsoever has to be understood according to the logic of sensibility; that is, anything whatsoever exists in relation to the possibility that it suffer not being itself, or suffer being taken outside itself or its identity, understood as that which makes it what it is. In this sense, nothing exists that is only itself; every entity is always also not itself, "containing" an outside that somehow haunts its identity. In the words of the delirious, dreaming D'Alembert: "All creatures intermingle with each other, consequently all the species… everything is in a perpetual flux. Every animal is more or less man; every mineral is more or less plant; every plant is more or less animal.

The activation of sensibility means a passage through an outside, which for Diderot is a passage through madness, in its being completely undetermined by any identity or preexisting condition; that is, it is completely non-teleological and, in a way, is nothing but the very fact of activating that which has neither beginning nor end: the activation of the in medias res.'

'The fact that there's a new nightclub and the club is not really ready, the building is not finished, well, all of a sudden, you see people's individual personalities coming out. You see? Do you have a piece of paper? I'm going to show you the structure I came up with myself. Do you have a second? Here, at the start of the film, I tell the actors to walk in straight lines, no curves or bends, so everyone follows the lines of modern architecture. It's all built like that, the maze of offices, the cubicles, it's the architect who decided that, and people go straight and then turn sharply, and turn again sharply. It's the same with the display rooms; no one can do any swerves or bends. Then we get to the nightclub, and already there is something there because the neon sign doesn't work properly and the direction isn't so clear. So, you get a sense that things are a little off, and then you can see from the architect's mistakes that the building is not finished. So people have to go around things, and then the neon sign starts working, but then you have a second swerve because people start dancing, a third swerve, and people are moving around and around, and, well, I'm not a painter, but you can see how it's like a modern painting. We end up with this merry-go-round, and you can see that it's the people in the film who have taken on their own identity against this background, they are living the way they want to. Do you see?'

'The disruptive experiences cited above illustrate why musicians diligently cultivate sensibilities to group interplay on the bandstand. By necessity, the process is a gradual one. Excited by their discovery of jazz, students initially seek opportunities to improvise at every accessible performance venue and in any group that will have them. They are, in the beginning, less particular about the partners with whom they form musical relationships, because they have yet to appreciate the subtle dimensions of interpersonal communication and the intricate meshing entailed in successful improvisation. Many are not immediately attuned to the exceptional moments of performances, nor acclimated to the extramusical experiences that accompany them. "I remember the first time I experienced that floating, out-of-the-body feeling," Leroy Williams recalls. "It was a number of years ago, when I was playing in Chicago. At the time, I didn't know what it was. I said, 'What is this?' and I backed off it for a minute." Charli Persip reminisces along similar lines. "The first time I ever got the feeling of what it was like to strike a groove, I was pretty young. At the time, I didn't have enough sense to realize that it was one of the few times I was playing smart. But I learned that later."

With growing sensitivity to the nuances of collective improvisation and a new perspective on earlier musical encounters, performers attach special significance to the support and emotional warmth they had formerly shared with players in particular bands. Over time, they increasingly discriminate in forming their associations. As in other kinds of human encounters, it is sometimes not until individuals have broken the bonds of one relationship to take up another that they appreciate how special were the qualities of the first. "There has to be a certain empathy among all the players in a group before the beauty in this music can really happen," Leroy Williams assets. "In some situations, everybody is trying to outshine everybody else. Once you experience how beautiful this music can be, and then you play with musicians who aren't up to your level or who don't have the same chemistry, then things don't happen in the music, and it's bad. It's like when you're used to champagne, and you're given beer."'

'Aurally this difference might manifest itself in a greater deliberateness, occasional stops and starts, and perhaps repetitions for obvious technical reasons. Or the difference between the two might not be aurally apparent at all. But it will be there and it lies in the improviser's relationship to what he is playing. He listens to himself in a different way. He might be much more analytical and much less involved in aspects of playing created by the impetus or the tension of performance. The playing might be much the same as when improvising but the focus of attention will be on the details of playing rather than on the totality, and what is being exercised is choice.'

'I have developed these conceptions of authenticity by setting them against what I argued are analogous moments in Wittgenstein and Heidegger: Wittgenstein's invention of rule following and Heidegger's investigation of anxiety. In both cases, we confront the worry that we have no good reason for going on as we do. For Heidegger, this was what McManus (2015a, 166) calls the 'Motivation Problem' that confronts Dasein in anxiety: in the absence of compelling reasons for pursuing projects, my choices, far from being resolute and authentic, seem either groundless and arbitrary or inauthentically grounded in das Man.

Here is one way of framing that dilemma. Inauthentic absorption in the one-self unduly constrains my responsiveness to my circumstances whereas the voice of skepticism or anxiety makes that responsiveness seem radically unconstrained: 'Anything—and nothing—is right' (PI §77). Responding authentically to our uncanniness means finding in ourselves a way of responding to our circumstances that is neither so sharply constrained as to be inauthentic nor so radically unconstrained as to be arbitrary. What does such responsiveness look like? Although Wittgenstein does not give Heidegger's explicit attention to the concept of authenticity, I think we find in his attention to unregulated play a model for thinking about the kind of responsiveness that authenticity requires.

We find a real-world model for this kind of responsiveness in musical and theatrical improvisation. Improvisers untether themselves from scripted instructions for how they should proceed but this does not leave them radically unconstrained: pace Harris (1988, 91), free play does not entail a 'free-for-all' in which any move is as good as any other. Actual improvisation is an exquisitely delicate balancing act that can collapse into chaos or banality unless players allow themselves to be guided by the continuously evolving play. The twin threats of chaos and banality are essentially the threats of the dilemma I framed in the previous paragraph. The improviser who falls back on merely conventional responses is boring and the improviser whose responses are entirely arbitrary turns the performance into an incoherent mess.

Performing the balancing act successfully requires responsiveness rather than control. Accomplished jazz musicians seem less to be making music than they are listening to the music that is flowing through them and their fellow musicians. Theatrical improvisers also place a high value on listening and discourage as destructive the ambition to control the direction of a scene. This kind of deep listening allows improvisers to avoid the twin threats of banality and chaos. Their attunement allows them to find responses to the state of play that are neither conventional nor arbitrary but rather answer inventively to the particularities of the situation.

The conventional responses of inauthentic Dasein manifest a coarse-grained responsiveness to the situation. At a high enough level of definition, every situation is unique, so falling back on what 'one' does manifests an impulse to assimilate this situation to ones that are similar to it. Skilled improvisers see what is similar while also being alive to the uniqueness of the situation.

What emerges from this model is an account of authenticity in which we are not so much agents as players.…'

'In the end it is ex tempore eloquence that is the primal manifestation of the rhetoric of the time. Philostratus searched, literally, for the person in whom "the waves of improvised speeches found their source [skhediôn … pêgas logôn … ek … rhuênai]" (482): the metaphorics of time is evidently a metaphorics of flux, of waves. The time of discourse and the time of becoming: this is the perspective—it has been remarked—from which the alignment of sophistics with Heracliteanism appears correct; "everything flows" in the world of those who speak. But what has not yet been understood is how ex tempore is said in Greek: skhedioi logoi, "improvised speeches," skhediazein, "improvise." The adverb and the verb indicate proximity, whether it be spatial (that of two warriors in close combat) or temporal (the approach of death, as well as the unexpectedness of an event); such that skhedia, for example, is the word used by Zeus in book V of the Odyssey to designate the "stout binding" [epi skhediês poludesmou, V, 33] of the ties as numerous as those that bind Ulysses himself to the mass when he sails past the Sirens. This conjunction of spatial adjustment and precarity, of temporal immediacy, makes up the approximative essence of the "raft" Ulysses fabricates to escape his love for Calypso. Improvised discourses are the rafts upon which man embarks along the course of time.'

'the specter of supreme disregard that lurks in the margins of their compositions'