Read First. Can you have multiple protagonists that work against each other, but aren't neccessarily one sided on who is right/wrong? Like two main characters that cause each other conflict, but the reader decides whos side they are on. They both are like each others antagonist, but they are also protagonists, with the story told from both of their points of view.
In such a case, there would be no concrete antagonist among the characters, each taking their turn as it were. However, the antagonist doesn't always need to be a character. The central problem itself can be the antagonist. It's really a role you can't avoid.
In almost every instance there needs to be conflict or some goal to obtain with an obstacle to overcome to keep a reader engaged. I'm sure one can find a novel here or there that meanders with description and flits from one scene to another without conflict or seeming reason, but I can't think of any that I've read. How you define the 'antagonist' or portray the conflict or struggle to achieve some goal or whatever, it's up to you. If your story includes two characters where neither seems to be a 'bad guy' but are at odds with each other... It could be two top notch students striving to obtain a scholarship for college. They compete but is either a 'bad guy'? Two women painting a masterpiece, each striving to be featured in a city-wide art exhibition... In the end it's how engaging the story is and how well the story is told that will make the difference.
TWErvin2 hit the right points. Conflict is almost always what is necessary for any story to work, not necessarily your everyday villain per se; there are a few exceptions, of course, but even then such exceptions have some degree of conflict or something similar to it. A classic way to describe it is by thinking about "Man vs. X" - is it "Man vs. Man", "Man vs. Nature", "Man vs. God(s)", "Man vs. Self", etc. The main character(s) or protagonist(s) have to be in competition or conflict with something, sure, but it doesn't need to be an actual other person. For instance, in The Catcher in the Rye, the main conflict for the protagonist, Holden, isn't really against anybody - sure, there are people he has a bad relationship with or starts fights with, but the true antagonist all the time is really himself; he's trying to find a purpose and meaning to life, and he himself struggles against his own limitations and internal problems throughout the novel. Survival stories are also another example - think Robinson Crusoe or the like; the "antagonist" here, usually, is in actuality nature, which the protagonist must struggle against to survive or else face certain death.
Ahh, I see. An antagonist doesn't even have to be a character. I was speaking of two protagonists antagonizing each other.
Of course you can. The important thing to understand ist that plot depends on opposition to create tension. The opposition can consist of characters, or it may be a general obstacle or force. Please read What is Plot Creation and Development?
In my novel I'm editing right now there's no villain. Everyone's friends with everyone else, and the plot is mostly about how one of the girls goes missing, and her friends go drag her back out of love and caring and blah. The place she vanished to isn't good or bad and the things that happen there lead to no punishments - in a way the ending is worse because no one feels resolved by it, since all that happened was random crap, and some of it was good and some bad, and everyone mostly feels like they'd have been better off just not getting involved in the first place. There is no one to blame for what happened. There's a lot of tension between the characters though - it's teenage girls, and their politics of who likes who more and why are more than enough to keep them sniping back and forth at each other in conversation and maybe not give conflict, but to keep it from being all lovely and annoyingly bland. So far I've got 8 books planned and 4 written or started, and there are no villains in any of them, just the main characters messing up their lives and arguing with each other. Sometimes you make it seem like there's a villain, like, assuming someone is behind something which no one actually was, or presenting a character *like* a villain, but revealing they weren't.
I see where you are trying to go with this; I also admit you have a valid point. I think you have got my intentions wrong though. I plan on having plenty of conflict and such. I just don't want to be one sided about it and I also want to tell the story from multiple points of view. Let the reader decide who is right/wrong. Your response is noted though.
The antagonist doesn't have to be evil or bad; he/she just has to be the force that's working against your protag. The antag could be bad weather, a crowd, too little time, a murderer, the cops, a well-meaning parent/guardian who holds the character back, a class that's too hard, a boss at work, distance, anything. So yes, your antag can be a good person, and you can use shades of gray rather than black-and-white clear-cut good/bad roles.
I agree with Cogito. The antagonist does not need to be a person or a thing. It could be man verses nature or man verses himself. Lots of good books written about self struggles. As for: I love this idea. Might be hard to write though.
You could also toy with perhaps the antagonist isn't really this second character at all, but a strong character flaw of the true protagonist. For example, perhaps they are addicted to drugs and this inhibits them from doing what they really want, or perhaps they are extremely hot-headed/stubborn, or they are afraid of success. You could present the second character as a possible antagonist, but in the end the reader realizes that Chris' real enemy is himself. Just an idea.
The idea is intriguing, but it would be hard to execute. It would be difficult to write both characters the same (objectively speaking), since you're bound to feel more connected to one of them. And if they are both essentially good guys but working against each other not for a competition or higher goal (that is worth it in the readers eyes), I'd probably toss the book with the comment 'they're both idiots' - so, have a few people proof read the first couple of interactions, before doing he whole thing. Oh and the reason they antagonize each other could be the actual opposing force, making the reader happy if they finally combine forces to succeed. If one wins out and i liked the other character better, I'll grumble at you...
I didn't say I wouldn't make one bad, I just didn't want to be obvious about it... I have a few ideas up my sleeve. I am guessing this kind of thing isn't common and I actually thought of an original yet interesting idea on my own?