|It is not very difficult to establish
the initial interest of Duchamp about temporal perspective. Looking at
his works is convincing enough, and if some doubts were still left, then
listening to Duchamp himself would quickly fade them away
"My problem was cinetism - movement - and them [the cubists] did not ever mention it, because they did not use movement in their paintings. Cubism is a non-movement" 
Cubism appears at first as a new approach of the perspective problem, and hence, just as classical perspective, it implies some sort of representation of movement. Why does Duchamp say that cubism is a non-movement, then?
The classical perspective suggest the movement of the mind, it opens a space for it, a field for its action. And the trap is precisely in this freedom. The mind may - must - move from one object to another, wander from the foreground to the background. It must ultimately be convinced of its own freedom. As a matter of fact, it is only free of chosing among the objects that it is given. In the classical perspective, the mind may dance as it likes, provided all its paths drive it precisely where the painter wanted.
Cubism is a perspective the center of which is the object. It addresses and indicates an organization of the object rather than an organization of the space. It proposes a representation of the multiple aspects of the object into a synthesis that integrates and unifies them all, but into which the only movement of the mind which remains autorized consists into endlessly moving in circles around things. And in this, cubism was actually prophetic.
A symptom of this assault against the activity - that is to say, against the freedom - of the human vision may be illustrated by the way Duchamp's work "Nu descendant un escalier n° 2" was not shown at the Salon des Independants: "on the day before the opening, Gleizes asked my brothers to suggest me to change at least the title, because according to him, and after discussion with Delaunay, Le Fauconnier and Metzinger, the canvas was not cubist according to their meaning of it - it was so much outside of the axis of cubism that they felt compelled to interfere... A nude never goes down a staircase - a nude is at rest, you see... Even their little revolutionary temple, could not understand that a nude may go down staircases... So I said nothing. I said well, well. I took a taxi to the exhibition, I took my painting and I took it back home. So that it was never exhibited "aux Independants" in 1912, although it is listed in the catalog" 
"I considered art from a wider
angle. People used to discuss at that moment about the forth dimension
and non-euclidian geometry. Most of the time it was only amateurs points
of view... But despites all our misunderstandings, these new ideas freed
us from the conventional language - from our bar and studio flatnesses."
Whereas the cubist perspective is central, all looks and all absence of mind being like swallowed in the object, Duchamp's work is immediately reflexive. The subject is not an object anymore but something like the very action of stripping off all objects: a nude attempting to think its own movement. In Duchamp's painting, there is a man who walks.
But not satisfied with only studying time in the perspective of its passage, Duchamp also studied it the perspective of its depth.
In 1912, something happens to Duchamp which is bound to happen to anyone who is playing with chronophotography: he starts wondering about what happens between 2 images of a series.
Mathematically speaking, this is equivalent to wondering about what happens between Zero and One. The mathematical answer, as it was given once to me by a friend to whom I had addressed this delicate question is : "It all depends on the sequence you choose". This answer is essentially based on the fact that the set of real numbers may be built from the set of all sequences of rational numbers (fractions), and additionally based on the fact that the set of real numbers between Zero and One is just as rich and just as big as the entire set of all real numbers. More precisely, there is, at least, between Zero and One, a non denombrable infinity of stories that may be written with a non-denombrable infinity of words. Which really makes quite a lot of tales.
Duchamp graphically express this solution in "Le Roi et la Reine entourés de nus vites" (1912). It is quite easy to see that Duchamp first adds the depth of classical perspective to the pure linearity of the passage of time as it was expressed in his previous works. The two instants at which the photographies are taken are represented by the King (static aspect, associated with past) and the Queen (dynamic aspects associated with future). In between, the nudes are moving like wind, like life, like the hand of Duchamp on the chessboard.
However, "Le Roi et la Reine entourés de nus vites" (1912), yet does not show how the transition between the King and the Queen happens. It only shows a sudden awareness of Duchamp about the fact that "true life is somewhere else" . The proposed solution is not very satisfying, because it only shows the transition between the King and the Queen as a continuous movement.
Duchamp then attempts a synthesis in "Le Roi et la Reine traversés par des nus en vitesse" 1912, which superposes both approaches. The previous trajectory of the nudes between the King and the Queen is quite clearly visible but also a transversal trajectory which interferes, feeding the initial trajectory with the flesh of an encounter. In other terms, the microscopic architecture of time, as it appears in this painting is encounter. Schematically, the King transforms into the Queen because of the random interaction of two trajectories which could not priorily be revealed by the successive pictures of chronophotography.
The analysis of temporal continuity that is leading
Duchamp at this moment is the same as the one illustrated by the Tadpole
Paradox: it is quite easy to see the difference between a tadpole and a
frog, but it is much more difficult to spot the precise moment when the
tadpole becomes a frog.
"La Mariée mise à nu par les célibataires" (1912) shows very clearly the Bride - in other terms Creativity in action - dazzling with all the splendour of her vivid reality, the two bachelor ghosts who infinitely strive to strip her of the dead skins of her successive packagings.
As Duchamps says: "I consider painting as an expression means and not at all as the exclusive goal of a life, in the same way that I consider colour as a simple expression means and not as the goal of painting. In other terms, painting must not exclusively be retinian or visual ; it must also be interesting for the grey matter, our appetite for understanding... I never wanted to restrict myself to a narrow circle and I always tried to be as universal as possible."  .
Yes indeed! And it is not very likely that such a level of intellectuality had ever been reached in a painting before. As it is not very likely that it has ever been reached very often after.
The rest of the adventure connects reasonably well with the Ready-Mades episode: since the approach towards reality can obviously not be attempted by ordinary pictural means any longer, it become necessary to use what is the very mediation by which knowldege acquires some effectivity in reality, that is to say the instrument, the thing, the machine. Duchamp had priorily tried this approach by stripping bare a "Coffee grinder" from the inside in 1911.
 - "La mariée mise à ni chez Marcel Duchamp même" - Arturo Schwarz - P27
 - "La mariée mise à ni chez Marcel Duchamp même" - Arturo Schwarz - P26-27
 - "La mariée mise à ni chez Marcel Duchamp même" - Arturo Schwarz - P35
 - "La mariée mise à ni chez Marcel Duchamp même" - Arturo Schwarz - P30
 - Arthur Rimbaud
 - "La mariée mise à ni chez Marcel Duchamp même" - Arturo Schwarz - P31