Some say that you either like Woody Allen movies or you hate them, and although I find that I like some and not others, I can understand the idea.  Allen is the writer and director of Midnight in Paris, and although he does not appear on the screen, his mark is definitely on the film.  Not only does it echo of some of the cinematic flavor and fantasy strangeness of The Purple Rose of Cairo, Owen Wilson in the lead role of Hollywood scriptwriter and frustrated novelist Gil Pender so often seems to be channeling Allen's acting style from such films as Manhattan Murder Mystery one can easily imagine a young Allen in the role.  Yet it is a thoroughly enjoyable film which wears its message on its sleeve, and uses time travel elements to explore it.

The message, in a nutshell, is that there is no "Golden Age".  Visiting Paris in 2010, Gil dreams of the city in the "Golden Age" of the 1920's, and then visits it, meeting all the famous people--Cole and Linda Porter, F. Scott and Zelda Fitzgerald, Gertrude and Leo Stein, Ernest Hemingway, Pablo Picasso, Djuna Barnes, Archibald MacLeish, Salvador Dali, Luis Buñuel, Man Ray, Alice Toklas, T. S. Elliot, Henri Matisse, Josephine Baker, Jean Cocteau, William Faulkner, and matador Juan Belmonte, as he is drawn into the inner circle of artists and writers of the period.  He makes several trips, building a relationship with a girl, the (fictional) oft-painted lover of several artists, Adriana, while his relationship with his fiance in 2010 gradually dissolves over their differences.  Then, in an unexpected twist, he and Adriana travel back a bit further to the 1890s, La Belle Epoque, the era Adriana imagines is the "Golden Age".  Here they meet Henri Toulouse-Lautrec, Edgar Degas, and Paul Gaugin, and find that Degas and Gaugin think their age is devoid of imagination, and that they wish they were part of the real "Golden Age" of the Renaissance.  Gil realizes that the notion of a "Golden Age" is an illusion, and that he will never be a truly great writer until he can get past it.  Adriana stays in the past, but Gil returns to the present, ends his failing engagement, and decides to settle in Paris in the present to finish his novel.

There is more to it than that, of course, but this gives us a framework.  Gil travels back to the 1920s five identifiably separate times, and from the last of these makes a nested trip to the 1890s, then stops in the 1920s on his final return to 2010, creating six distinct anomalies; additionally, a private detective hired to follow him takes a wrong turn and travels to pre-revolution Versailles Palace, possibly a seventh anomaly, depending on how we reconstruct events.

There are a number of significant quirks in the story which need to be considered in detail.  It is clear, given the replacement theory assumption of an original history in which no one travels from the as yet unwritten future, that each of these trips changes the past.  At issue is whether the changes are in any way significant.  This is very difficult to evaluate.  In one sense, Gil is interacting with some of the most influential creative minds of the time, and is bound to impact them and through them the rest of the world.  In another sense, it is not clear that he does much that would change who they are or what they do, and thus he is very nearly an observer.  Yet there are points at which he, or one of the other time travelers, might be making an impact that ought to be considered.

Because of the butterfly effect, we can never be certain that a time traveler will not have disastrous effects on history.  Although the notion does not come from the Ray Bradbury story in which a time traveler destroys the future by killing a prehistoric butterfly (A Sound of Thunder, poorly represented by the movie version), it is an example that is serendipitously appropriate.  It is possible that Gil's perspiration altered the humidity enough to change the weather, or that the kinetic energy from his footsteps disrupted a seismic fault, that the tiny contributions he made to events and social interactions in the 1920s reverberated into great changes.  However, in his first visit he does nothing that has a very high risk of changing anything.

That might sound like overstatement, given that he interacted with many of the most famous and artistically influential people of the era, and if he impacted their work in some way the impact might matter decades later.  Picasso might not have painted his Guernica, or Hemingway might have attempted to write a science fiction book about a man visiting from the future, and the world changes as their influence reaches others.  In the case of the first visit, though, he does not do much. He meets the Fitzgeralds, and the Porters, and Hemingway.  These are famous people quite accustomed to meeting people who know who they are and are terribly impressed with the image and the fame and the wealth.  They attempt to make him feel comfortable and accepted with a practiced ease which suggests that they frequently interact with fans and try to disabuse them of that idolatry.  He promises to bring his book for Hemingway to give to Gertrude Stein, but at this point he has not said more than that it is about a man who works in a nostalgia shop, which he had to explain.  He leaves, intending to return with it, and finds himself returned to his own time.

For Gil to arrive in his own time, all of history from the moment he leaves Hemingway in the bar to the moment he arrives in 2010 must be written, without the subsequent arrivals that flow from his subsequent departures; those will rewrite history yet again, inserting him into moments in which he did not appear.  That of course means that Hemingway is expecting him to return with the book and he never does; but that, too, is probably something that has happened before and will happen again for him.  He will write it off as just another aspiring author who lost his nerve, or became too busy.  Outsiders become acquainted with them and then fade away again, always at different rates.

The only part of that first visit that might be problematic lies in the means of travel, and that is something we will have to consider carefully, because if it works the way we are inclined to believe it is potentially disastrous, but if it works a different way it is no problem at all.

there was nothing about Gil's first visit to the past that was fatal to history, unless it was the means of time travel itself.  That is what grabs our attention now.

Gil waits by an old church somewhere in Paris, and as the clock strikes midnight a 1920s-era Peugeot limousine pulls up and he is invited, the first time and several other times (on one occasion he asks for a ride) to join the passengers.  The car then delivers him to the past.  This is repeated, with variations on who is in the car, each night.  Similarly, one night in the 1920s Gil and Adriana are seated alone on a bench when a horse-drawn carriage arrives and the occupants urge them to come with them, which takes them to Maxim's in the 1890s.  It seems as if because they are people who wish to live in the past, a car comes from the past to collect them and take them there.

It is simple to say and readily admitted that the means of travel to the past is magical; that does not mean that it does not have rules, only that its rules might be different.  What is not different is the effect of traveling in time.  The critical question here is, does the car drive them to the past, or are they already in the past when the car arrives?

This would not matter if it were simply a supernatural car with a supernatural driver that appears and travels to the past.  The reason it is problematic is that it contains natural people, who on at least one occasion step out of the car themselves onto the street where Gil awaits.  It matters because those who ride in that car include at least Ernest Hemingway and T. S. Elliot, and if they have traveled to the twenty-first century, even briefly, they have vanished from the twentieth, severely altering history.

We discussed this in connection with Back to the Future II, in which Doc takes Marty forward thirty years to attempt to help Marty's son.  Because Marty leaves 1985 and leaps to 2015, he never marries and has no son; they arrive in a future in which there is no other Marty and no son, and it is not until Doc restores Marty to his own time that the future can occur.  In exactly the same way, once Hemingway, or Elliot, or anyone else, leaves 1920 for 2010, he skips the remainder of the twentieth century and is absent from it.  Anything he would have done in that time he never did.  Further, because these are famous people, there is now a mystery concerning their disappearance--similar to Amelia Earhart, or Jimmy Hoffa, with theories concerning what happened to these people last seen getting into an unidentified yellow Peugeot limousine somewhere in Paris.

Of course, in one sense they come right back; they were gone for such a brief time no one knew, and perhaps they never knew that they had left.  Yet in order for them to arrive in 2010, all of the history from the moment they stepped into the vehicle until the moment Gil does so must pass without them; they drove across time, and like Buck Rogers or Redferne or the famous people grabbed by Bill and Ted, they were not part of it.  That means that Gil's knowledge of them would include nothing after their 1920 departure but the fact of their mysterious disappearance.

The alternative is that the car does not travel to the past, but the traveler has already moved to the past when the car arrives.  This is complicated by the fact that there are sometimes other vehicles parked on the street, and in one instance a modern vehicle which attempts to follow the Peugeot, but it must be assumed that for just a moment the entire street moves into the past, returning to the future after the vehicle from the past leaves.  This is much simpler temporally; a street which no one will miss vanishes for a moment from our time and moves to the past, then returns within the minute, no one the wiser.  Those in the vehicle might have noticed some odd aspects, but it is dark and they are preoccupied, so the anomaly caused by the street traveling is minimal, and we save time, even though it is more colorful to imagine it the other way.  After all, if a Delorean pulled up outside your house and a man with wild white hair insisted you get into it, you would probably expect to travel to 1985.

Having addressed the transportation issue and reconstructed the changes from the first trip, we can continue examining effects Gil has on the past in his subsequent trips.

The second time he boards the car, Hemingway is in it, and it takes him directly to Gertrude Stein, where he also meets Pablo Picasso and the girl, Adriana.  Gertrude reads aloud the opening words of his novel, which all hear and Adriana immediately praises because she, too, believes in a "Golden Age" in the past, which for her is the 1890s.

He leaves the book there and returns to the future.  He never returns for the book in this history.  Gertrude Stein will finish reading it, and she and Hemingway will wonder what became of Gil Pender, whose novel was an interesting twist on science fiction but needed a bit of work.

At issue is whether having read the novel Stein will have changed in her thinking in some way that influences her reactions to writing she reads in the future.  Will she compare the works of other writers to this unpublished novel by an unknown and now untraceable Gil Pender?

Beyond that, several others were present.  Did the words influence Hemingway, such that one of his as yet unwritten books will draw on the notion of someone trying to recapture the past?  Will there be a new painting by Picasso, or a change in an existing one, or perhaps a shift in his style, and if so will it influence other surrealist artists?  We know that it had an impact on Adriana, and she has a penchant for attracting and influencing famous artistic men.  Modigliani, Braque, and Picasso have already been her lovers, and Hemingway has taken an interest in her.  Who will she influence, and will the impact of those words, as they caused her understanding of her own interest in the past to coalesce, change the effect of her influence?  She already leans in the direction of a love of the past, and she already influences the artistic and literary society of the world.

It is not certain that change has not happened.  Most dramatically, though, it must be after this trip that Adriana makes the note in her diary that she has fallen in love with him.  His next trip is the one on which he casually mentions his fiance, and she leaves him, and so she would not have written it after that.  It must have been while chatting in Stein's sitting room that she fell in love.  That's further problematic, because it is going to change her relationship with Picasso (her current lover).  Perhaps she did not before this realize that she was not in love with any of her lovers, or perhaps she thought it something that would never happen to her, or even a romantic fantasy that never really happened to anyone.  Suddenly she is in love with someone she only just met, whom in this timeline she will never see again, and all she will ever have is those words in that book.

That, though, leads to another issue.

Gil Pender's second trip to the past is the first one in which he leaves a copy of his novel in the past with Gertrude Stein.  He does this more than once--she has not finished it on his third trip, so he leaves it with her again--but any time he does it we have to ask the question of what happens to a manuscript of an unpublished novel abandoned at the Steins' residence.

We must understand that it will be there for years, and that already it is clear that she won't tell others not to read it.  When Gil does the revisions for her consideration, she gets Hemingway to read those.  It is not only possible but probable that others will read it over the decades ahead.

Even if no one steals the work outright, writing a revision and publishing it as his own work, it is likely to have some influence on those who read it.  Little ideas might be borrowed, even inadvertently, and become parts of other works where they will get more exposure, ultimately becoming part of the literary landscape.  At some point they become cliche; Gil Pender does not use them because what were in the previous history his original ideas are now cliches borrowed from the book he left in the past.  That, though, means they are not in the book, and not borrowed, and might again be his original ideas.  We potentially have an infinity loop, two alternating histories each of which causes the other.

Perhaps not.  Perhaps Gertrude puts the novel away and it remains forgotten, eventually trashed in later years.  Perhaps a few read it but find nothing inspirational in its pages.  It is again something dangerous but not fatal, something that might destroy the future but is not guaranteed to do so.  As compared with his first trip the probability is considerably higher, but it is nowhere near a certainty.  What could have happened, even what is likely to have happened, are part of the analysis, and show us whether we are close to disaster; but since the story can continue if this does not happen and the story does continue, we assume that it did not.  For whatever reason, the manuscript Gil Pender leaves in the past never impacts any other writer sufficiently to impact him in the future.

However, he is getting bolder in his efforts to influence the past.

Long before it was connected to a line of video games, Zelda was the name of author F. Scott Fitzgerald's wife.  She is, in this story, the first person in the past to befriend Gil.  However, on Gil's third visit to the past, he does something significant, not for the fact that he did it but for the fact that there must have been a history in which he did not do it, and that would have been very different.

It is believed that Zelda Fitzgerald was unstable, and she may have attempted suicide more than once.  There is no record, however, of her attempting to drown herself in the Seine.  Of course, it does not happen, because Gil and Adriana see her and prevent her from doing it.  The problem is that there was an original history in which Gil was not there, and a first altered history in which he was not there, and a second altered history in which he was not there.  Zelda must have landed in the river in all three of those, and her survival (the history we know) is thus an altered version.  She must have thrown herself in the river, unseen, in the original history.

It is difficult to imagine any event which would have had more impact on the literary career of F. Scott Fitzgerald than the death of his wife, save perhaps his own death or disability.  His writing would be different; it often drew on her personality and their relationship, by all reports.  He would have written different books; and being one of America's great twentieth century authors, he would have changed twentieth century literature in the process.  If she drowned, everything changes; or more precisely, if Gil saved her from drowning, he changed everything to be what we know.

There is no basis for thinking that she would not have made the attempt absent Gil's presence.  She does so from jealousy, thinking her husband is flirting, or worse, with some unnamed countess.  We never met the countess and have no reason to think that anything Gil did would have caused that.  Thus we are faced with the probability that Zelda left the party in despair because of a belief that Scott did not love her, and threw herself in the river.

We also cannot suppose that someone else saved her.  The only people who seem to be there are Gil and Adriana.  If Gil has not made his third trip to the past he will not be there; and Adriana is there only because she is strolling with Gil.  Thus no one sees her jump, and no one is there to save her.

It is possible that there was an original history in which Zelda died in the 1920s, Scott grieved her loss and then continued his career, either as a widower or more likely marrying someone else, writing different books and following a different career path.  The history we know, then, is the revised one, in which Gil saved Zelda's life.  It would be peculiar that he knows so much about the Fitzgeralds but was unaware that Zelda drowned in the Seine in the 1920s; of course, once he has saved her, all of history is rewritten including his previous visits to the past to incorporate the revised knowledge of the Fitzgeralds, and he saves her without knowing that this changes history.  There might be significant impact from this, if it were so.

On the other hand, it is possible that Zelda threw herself in the river and climbed out, cold and wet and feeling foolish, went home, changed her clothes, and never mentioned the incident to anyone.  Gil only thinks they thwarted her suicide because they thwarted her attempt.  On the other hand, his assurances that Scott loves her (which at this point are undoubtedly true) might help their relationship; and the introduction of valium is also going to help her.

It is alternatively possible that somehow Adriana's presence at the party prevented Zelda's departure, interacting with either the Fitzgeralds or the Countess.  In that case, Gil's presence both causes and thwarts Zelda's suicide attempt.

It is at this point that Adriana discovers that Gil is engaged, and decides to separate herself from him.  He never returns in this timeline, so she never reneges on that decision.  However, he threatens to impact history in another serious, if less dramatic, way as he joins three friends in a restaurant.

Woody Allen pokes fun at Salvador Dali, representing him as fixated on the rhinoceros.  The animal is highly symbolic in Dali's artistic view, and although the joke denigrates this, it is funny.

It is the context of the joke, though, that is serious.

Dali apparently met Gil at the party at Jean Cocteau's earlier, and seeing him in the restaurant (where Adriana just left him) asks him to sit.  They are joined by movie creator Luis Buñuel and photographer Man Ray, and in the course of conversation Gil tells them of living in two times and being in love with two women.  It is joked that this makes perfect sense to them because they are surrealists.  However, the fact that it makes sense to them makes it more problematic:  he just gave them ideas that they recognize as potentially valuable to their own creative processes.  Buñuel in particular, a filmmaker, now has the suggestion of a story about a man who comes from the future and falls in love with a woman in his own past.  Man Ray is also clearly trying to imagine how he would capture this aspect of living in another time in a photograph.  Perhaps Dali is trying to envision a trans-temporal rhinoceros.  They have been given an idea, one which fits well in their view of reality, which they might incorporate in future artistic efforts.

This potentially alters the directions of their futures, and of everything they have not yet produced.  Dali might never paint his Last Supper; Ray and Buñuel's influence in photography and film might take new directions and abandon old ones.  An artistic career is very like a journey, in which changing one next step changes many of those which follow:  because he did this, he will never do that, or not unless and until the trail on which this puts him runs cold and he remembers something he was going to do years before.  The delay then puts those creations in a different context, a context altered both by the delay itself and by the cultural impact of the other trail.  What has been done always influences what will be done, even in the commercial world:  Paramount revived its forgotten franchise with Star Trek:  The Motion Picture in 1979 because they were looking for something like Star Wars just released in 1977 by Twentieth Century Fox; George Lucas was funded for Star Wars by an executive who loved Universal's 1973 American Graffiti which he had written, and he parlayed the success of the sci-fi blockbuster to fund the cutting edge special effects company Industrial Light & Magic, making possible a new era in movie and television effects including hundreds of titles from Battlestar Galactica to The Neverending Story to The Avengers.  One change in the career of a major artistic influence can have vast repercussions.  The introduction of so compelling an idea into the minds of three leaders in the surrealist movement could have changed the world in ways we cannot estimate.

Yet again, apparently it did not; or if it did, we do not see the impact.  If Dali or Buñuel or Ray ever did anything about a man living in two times, it does not appear in what we know about them today.  Thus again we have actions which might have had serious consequences not changing anything.  The story is still possible.

Hemingway had previously invited Adriana to travel with him to Africa, to hunt wild animals.  When Gil makes his fourth trip to the past and reaches the Steins' place, he learns that she has accepted the invitation and is not in Paris nor indeed in France.

This might be significant.  Nothing is mentioned historically about Hemingway hunting in Africa until the 1930s.  Of course, Allen might be playing fast and loose with his characters, giving us the image we have from the distant future and so telescoping decades of "this is who he is" into a momentary snapshot; but the fact remains that Hemingway seems to have traveled to Africa at this point in the film because he has persuaded Adriana to go with him.  The problem is that the only reason we can see for her to have ended her affair with the (married) artist Picasso and begun one with the (also married) author Hemingway is that she wants to escape Paris and the broken heart she has from her discovery on the third trip that Gil is engaged.  Had this not happened, she probably would still be ignoring Hemingway's bravado and inuendo, maintaining her connection to the painter.

That means that Gil has changed history, altered the lives particularly of Picasso and Hemingway, and incidentally of all those who know them--Gertrude Stein trying to talk Picasso through the shock, and the other friends of Hemingway.  Further, this is no small matter.  It is generally thought that Africa had a major impact on Hemingway's thinking, and through that his writing.  His successful non-fiction Green Hills of Africa is only one of the works arising from this experience.  Now we are moving the experience to an earlier decade.  Not only will it impact his work sooner, it will be a different experience, the experience of a younger man in different circumstances at a different time for a different reason.  He will write different books and different stories.  Thus not only the world but Gil Pender himself will know about a different Ernest Hemingway.

Certainly this changes history, causing an anomaly; but does it disrupt events sufficiently as to undo time itself?

It is certainly possible that Hemingway's books have changed, and that everyone who was influenced by his writing is influenced otherwise; that may have a severe impact on the world, and on Gil Pender.  We know that he idolized the writers of this era, including Hemingway, and his knowledge of the lives and works even of some of the less famous ones is impressive.  We cannot estimate the impact the works of Hemingway have had on him, nor how that impact would change if they were different works.

Yet at the same time it might not matter.  Hemingway is one of the several famous people attracting Gil's attention, and he is already a famous writer and part of that Paris scene.  It is not Hemingway in particular but the entire artistic climate that causes Gil to love the 1920s.  Further, he did not initially decide to go see Hemingway; he was offered a ride in an antique car and found himself at the bar where Hemingway was drinking.  The essential framework of the story is preserved, even if Hemingway's works (not to mention Picasso's, who lost his lover in this, and those they influenced) are altered.  Unless Gil loses his love for the past, the story is preserved.

We now come to an event in the future that is caused by an event in the past caused by an event in the future; it is not a major problem, however, because it is easily resolved.  At issue is Gil's discovery of Adriana's journal.

It is, of course, the film's remarkable coincidence; every film is permitted one.  He is wandering through Parisian nostalgia shops and stumbles on one old book which he examines, and despite the fact that it is written entirely in French and he does not know a word of the language and has never seen anything Adriana has written, he recognizes it as hers.  He takes it to someone to translate, and so hears that she has fallen in love with him, and a story about him giving her a pair of earrings.  He thus acquires (after some slapstick) a pair of earrings to give her, which ultimately he does.

It might appear that we have a predestination paradox, that he gives her the earrings because she reported having received them; but it is much simpler.  Her journal reports only that she dreamed that he gave her earrings; he is attempting to make her dream come true.  He reads no further in the book, so we do not know whether three pages later she would have written about receiving the earrings; whether he gives them to her or not, she had the dream before that, and her journal will not be altered by the gift at that point.  Whether it would be altered later is more complicated.

The gift itself is also complicated.  Had he given her his fiance's pearl earrings, perhaps it would not have been noticed; but he purchased earrings from a shop, and it is not entirely clear of what they are made or how.  In fifty years they might be grandmother's favorite earrings--but they might also be deemed fraudulent at some point, when examination proves them to have come from the modern world.  Even if no part of them is plastic, modern manufacturing techniques will have left their mark on them.  They are a displaced object temporally, not so bad as finding modern eyeglasses in an archaelogical dig, but still something that could raise questions.  However, we do not know much about the earings themselves, and if they are hand made of natural stones, they might pass most tests and never be examined closely enough to discover the problem.

Returning to the journal itself, Gil is going to take earrings back to Adriana, and when he does so she is going to travel to 1890, leaving the journal in 1920.  She has not yet done this, and therefore the journal, in the original timeline, must continue.  Her comment about falling in love with him must predate her discovery, on his third trip, that he is engaged (or she would have included that).  It logically must continue with the heartbreak of her discovery and the details of her trip to Africa with Hemingway which was occuring during his fourth trip.  Since in that history he does not return with the earrings and she never sees him again, the book will continue until it is filled and she sets it aside.  Yet the night he gives her the earrings she changes that.  They immediately leave for the past, without the journal, and she stays there.  The journal is never finished and never stored wherever she originally put it.  That changes the contents, and it might change the location--we know nothing of what happened to Adriana in the history in which Gil never brought her the earrings, but we know she moved about quite a bit.  The odds of the journal being in that same bin ninety years later are astronomically against.

However, as noted, this is the film's remarkable coincidence, and the fact that it is the more remarkable that it should be there at the conclusion of both histories is only a matter of degree, given that it was remarkable he would find it at all.  We could only guess how it got there, who had it when, and so we cannot say it could not have come to him that way again.  It is improbable but not impossible, and if it does not happen history ends (when he does not take the earrings to her), and since history does not end, it must have happened.

Gil's final trip to the past is complicated in several ways.  One of those ways is that he makes a nested trip, leaving with Adriana from 1920 to 1890; another is that a private detective attempting to follow him lands in seventeenth century Versailles.  There are problems with that; but the first problem is sequencing our trips.

Ignoring the detective for the moment, Gil travels from 2010 to 1920, and begins creating the history forward toward 2010; this is interrupted, though, while it is still 1920 (the same day), as he leaves with Adriana for 1890.  Assuming that the mode of travel is not a problem, we interrupt the advance of history and scroll back to 1890, then work forward again.  Adriana stays in 1890 (which we will consider later), and Gil leaps over the history she creates to return to 1920.  He finishes his work there, and goes home again to 2010.  We thus have an anomaly within an anomaly, almost as if Gil traveled from 2010 to 1890 and back with layovers in 1920.

Unfortunately, we have a problem with the detective.

Part of the problem is that we cannot say with certainty when he leaves 2010.  He attempted to follow the Peugeot, but he lost it somewhere in time and traveled back further into the past.  If we are correct in our assessment of the mode of travel, the entire street by the church must have drifted back to 1920 and Gil's vehicle exited it; but the detective, holding back so as not to be seen, must have remained on the street while it continued back to the seventeen hundreds.  But we are not quite certain what happened still.

If the detective left 2010 at the exact same instant as Gil, we have one anomaly.  It drops Gil off in 1920 and continues to the 1600s, then works its way forward to 1920.  Then when Gil and Adriana go back to 1890 we have our nested anomaly in the second side of the bigger one, which then resolves to 1920 as Gil returns and continues to 2010.

However, we have the problem that the detective was following Gil, and so, as we saw in the problem with Star Trek:  First Contact, there is the possibility that he is creating a second anomaly.  In that case, things are more complicated.  If the detective leaves 2010 even a fraction of a second later than Gil, we have separate anomalies:  Gil travels to 1920, stays a few hours, continues back to 1890 with Adriana, leaves her there, then jumps back to 1920 and to 2010, history rewriting itself in his wake; at the moment he leaves for the past the anomaly resolves; but since he seems to arrive a significant time later than he departs, his return is delayed:  the detective travels to the 1600s, and all of history must resolve again, including Gil's last trip, before Gil can return to the future; any changes made by the detective thus become part of history on this last anomaly.

Those changes could be substantial.  Gil and Adriana rode in period vehicles, but the detective brought a car from four centuries in the future to an era in which science is exploring new frontiers.  Galileo was active as the century began, and Voltaire was born before it closed; Newcomen is alive mid-century and will build his steam engine before he dies.  Give these people an automobile from the future, and they will study it.  This could advance technology drastically:  light bulbs, spark plugs, and rubber tires are just the most obvious attainable new ideas.  Technology leaps forward half a century or more, and the world from which Gil comes is altered so completely Gil himself probably does not exist.

Or perhaps not.  Perhaps the car is mistaken for a broken abandoned carriage and hauled for scrap, leaving the universe as it is.  Since history does not end, we must conclude this is what happened.

Incidentally, it appears that the detective never returned to his own time; he must have died and been buried in the past.  This raises another question about time travel method which we will have to address:  how does Gil return to the present?

We know, as well as we need, how people travel to the past:  a vehicle appears and they accept the offered ride.  Yet how do they return to the future?

As with most magical time travel stories, the film avoids trying to explain how it works.  Army of Darkness, Peggy Sue Got Married, Harry Potter and the Prisoner of Azkaban, A Christmas Carol, It's a Wonderful Life, The Lake House, Premonition, Teenage Mutant Turtles III, and Triangle all exemplify this, that if it's magic we probably do not know why it works (although several also demonstrate that there are still rules).  We are left to examine the events and guess.

At the end of his first trip, he says he is going back to his hotel to get his manuscript.  He leaves the restaurant, and almost as soon as he is on the street everything returns to the future.  That suggests that he has to be away from the people in the past and intending to go somewhere that only exists in the future (the room containing his manuscript).

We do not see how it happens again, but we do see at the end of his second visit that he says he is going home, and thus it appears that what matters is the intent to return home, and then being away from everyone.

The alternative is that the return happens at a random moment over which the traveler has no control.  The first problem with this is that it never happens randomly--it always happens when Gil is done with his business in the past and wants to go back to the future.  The second problem is that if this is so, then Adriana cannot choose to stay in 1890, and will be brought back to 1920 probably at the same moment that Gil is--which apparently does not happen, as she is not with him when he reaches the Steins' apartment.  Thus choosing to return to the time from which you left and heading for a specific location within it is what causes the return trip.  Gil returns to the future whenever he chooses to do so, and Adriana remains in the past because she wants nothing from the future.

The problem arises with the detective.  Doubtless driving into the seventeenth century will be disorienting, but to escape all he needs to do is decide he wants to return to the office and start in a direction he thinks might get him there.  He is lost in Versailles, and the guards have been called.  Yet he never returns to his own time, which means he must have been trapped in the past, perhaps caught by the guards and imprisoned and executed.  We might accept that if he were captured or imprisoned he could not attempt to walk home; yet at the moment he enters the hall, he is alone and running.  This means either our theory of how to return to the future is wrong, or he never for a moment thought, "I must get back to the office."

It seems, then, that we have no reasonable answer to how this works.  It is possible to choose to stay in the past, or to choose to return to the future, but it is also possible to be trapped in the past unable to return.  Thus either this aspect of the story was not fully considered, or we have been given insufficient data to resolve it.

Quite a bit happens in the scene in which Gil saves Zelda, including the important moment when Adriana discovers that Gil is engaged.  There is one other point that slips past, as Gil gives Zelda a Valium™ and attempts to explain what it is.  It is, of course, medicine from the future, a drug completely unknown in the Golden Age and common in the Modern Age.  As he is explaining this, he begins to recognize the implications of being in the past.

We know he recognizes them, because when he is in La Belle Epoque with Adriana it coalesces, that to stay in La Belle Epoque means to live in a time without antibiotics, and so too to stay in the Golden Age is to lose all of modern pharmacology and modern medicine.  The past sanitized is a wonderful place; the past actualized is terrible.  Life expectancy increased more in the twentieth century than in all prior recorded history, due primarily to advances in medicine and sanitation and nutrition.  Life is always hard for most people, no matter when or where you live, partly because real equality is impossible:  some will always have better lives than others, always on a bell curve such that most people know that there are others who live better than they do.  Everyone in the United States in 2010 lives better than anyone in the United States in 1890, simply because of the advances we have made.  The Vanderbilts and the Carnegies and the Rockefellers and other capitalist moguls had things we do not, but those did not include air conditioning, modern medicine, sewage treatment, not to mention television, computers, air travel, synthetic clothing, and plastics.  That Valium™ was Gil's first glimpse at the real wealth of the future and relative poverty of the past.

It probably is not serious otherwise, though.  The fact that Zelda took one dose of a future psychiatric medication at a time when she was upset, and it helped her, might encourage her to see a psychiatrist, but psychiatric medicine in her time has nothing comparable and she will undoubtedly be disappointed.  We might think she would devote some of her fortune toward the development of better medicines, but she never had much success as herself (and thus has no personal fortune) and her husband did not see much financial success after The Great Gatsby, so it's not as if there will be tremendous impact from this.  This also predates the age of celebrity spokespersons (it begins on a small scale with radio but does not come into its own until television).  She might like to see the development of more Valium™, but she is not going to be able to cause it.

So ultimately, when Gil gave the Valium™ to Zelda, it had more impact on him than it did on history.

Gil is not the only person to travel to the past.  As we noted, a detective leaves 2010 and goes to seventeenth century Versailles.  More significantly, though, Adriana goes to La Belle Epoque, Paris in the 1890s.  More significantly yet, she stays.

We cannot be certain that she stays.  We know only that Degas knows of a job for a costume designer for the ballet, and she plans to apply for it.  Her designs are bound to be avant-garde:  she studied with Coco Chanel, one of the great clothing designers of the early twentieth century who in 1890 is entering her teens but whose impact will continue well into the future, revolutionizing women's clothing.  Adriana will have an eye for the designs of the future, and in a progressive era like La Belle Epoch, the age of French Impressionism, such an artist will be embraced and successful.

There is the risk that she is ahead of her time, that she will fail because her designs are too futuristic.  Yet this is minimized precisely because she is designing for the ballet:  she will be a leader, not a follower, putting fashion images on the stage and on promotional posters which will then influence society in that direction.  As long as the ballet itself is successful, she is likely to be so also.

This then is likely to have three important impacts.  The first is on fashion itself:  introducing designs and concepts to the Impressionistic 1890s which would be progressive in the Surrealistic 1920s, particularly in fashion design leader Paris, France, will move styles in unpredictable directions.  What people wear in the future will be derived in part from the contributions drawn from the future by Adriana.

That cannot help but impact Coco Chanel.  She is a young teen in Paris, where Adriana's designs are about to hit the stage quite literally.  These designs are going to spark the girl's fashion-oriented imagination.  At least some of what Chanel would have created by 1920 will now have appeared in the 1890s, and she will already be building on those ideas to devise new ones.  (It is unlikely that Adriana's borrowing of Chanel's future work will prevent a creative genius of her caliber from finding new ideas from those; she managed to remain cutting edge for decades beyond that time.)  Chanel's work is altered, as she pushes the already reshaped envelope.

That, then, creates a sawtooth snap, because Adriana got much of her training in fashion from Chanel, who now is building on the ideas Adriana presented which came out of that training.  Adriana will learn something different from Coco, and her designs will in turn be altered in 1890, impacting fashion and Coco differently, impacting herself differently, and perpetually changing.  It might be that this history never resolves, because with fashion design there are enough variables that it might never be the same twice, and certainly never twice in succession.

In fact, the potential is here for Adriana to do something even more dramatic, taking a young Coco Chanel under her wing as a student, who in turn will become her teacher.  The feedback of such a loop is difficult to calculate.

This apparently does not happen, because Gil is able to return to a time in the 1920s after his departure, and again from there to 2010, so time is not trapped.  It is difficult to guess why not.  If Adriana did not get the job, she probably would not stay in the past; but if she did, she probably would have had the impact on fashion described.  Perhaps she returned to her own time, too late to catch up with Gil and tell him; but then it will be written in her journal, which he has.  Perhaps she stayed in the past anyway, struggling to find work or other means of support; perhaps she did not get the job as designer but was hired as an assistant, and stayed in the never-realized hope that she would one day create her own designs.  Whatever happened, Adriana faded to obscurity and never changed the world as she might have.

There are a number of loose ends to address still in Midnight in Paris.

There is a problem with the possibility of missing trips.  Near the end, Inez' father John mentions having hired the detective to follow Gil, and that it was reported that every night Gil got into a strange car and rode away, but that the detective never learned where he went and ultimately disappeared himself.  Yet as far as we can see, the detective followed him afoot losing him on his fourth trip and in a car on the fifth when he vanished.  Complicating it further, when Gil reaches Stein's on that fifth trip he is told that Adriana and Hemingway, who were in Africa when he made the fourth, have been back "for weeks".  That suggests that more time passed between trips in the past than in the future; but it also means that Gil made no trips between those or he would have known this.  The only reasonable resolution is that the detective saw him get into the car on the fourth trip and reported this, then on the fifth trip he reported perhaps by cell phone that Gil had again gotten into the car and he was following.  Twice consecutively hardly counts as "every night", but we can allow John to exaggerate.

We also have the genetic problem (as in Timeline) caused by Adriana's presence in the 1890s.  It is not even that she might marry someone or have children who did not exist in the original history; it is also that her apparently seductive presence is going to attract the attention of men whose attentions would otherwise be directed toward other women.  There is a very real chance that she will impact the gene pool.  However, this would be a ripple effect, with the ripple moving by generations.  She might impact Paris, but probably not Bordeaux where she was born in time to prevent her own birth; nor will she prevent the births of any of the Europeans, and certainly none of the Americans, who matter in the 1920s, because they all come from elsewhere.  Although many Europeans emmigrated to America in the early twentieth century, they congregated primarily on the east coast, and it appears that Gil and Inez are from California, so it is likely that they would not have been impacted by the changes.  Only Gabrielle is in serious danger, and she might be protected by social barriers--the impact will begin among those connected to the ballet, and take longer to reach the working classes.  So Adriana might impact the gene pool and yet not eliminate any of the people who matter to the story.

Glaringly, there is also a cute moment in which Gil gives Luis Buñuel an idea for a movie, about guests at a dinner party who at the end of the party are unable to leave, and social order deteriorates.  That film is The Exterminating Angel, written and directed by Buñuel in 1962, about four decades in the future.  Allen puts it here so that he can poke fun at the film by having its original creator ask the question everyone else wonders:  why do they not leave the room.  Our issue, though, is whether Gil impacts the future by giving Buñuel the idea for a movie which was originally Buñuel's idea.

The problem is that Buñuel is thinking about this idea too soon.  If he makes such a movie now, or within the next decade, it will be a different movie--for one thing, the actors will be from an earlier generation, but the ideas will be different as well, set against a different era in modern culture.  He would be unlikely to remake the movie later.  If he does not make it sooner, though, either it will be a different movie because he mused on it for decades, or it will be a foolish idea someone suggested to him that he discarded and never pursued.  Thus Gil's effort to become the inspiration for a brilliant film must go awry one way or another; and if that film is not made, Gil will not have the idea and cannot give it to Buñuel--creating an infinity loop.

This predestination paradox could be fatal.  Neither having the idea originate with Buñuel or with Gil resolves it adequately.  The only chance is that Buñuel forgets it entirely, and the idea comes to him some other way four decades hence.  As unlikely as that sounds, it is the only way there can be a future to which Gil returns.

And he does return, and none of the events are completely impossible, so we conclude that this has resolved to an unlikely but possible time travel story.