What if the opponent doesn't cooperate?

What if I memorize an opening, and the opponent doesn't cooperate? What if he hasn't memorized that opening, or just doesn't feel like following the book? 

What do you mean what if your opponent doesn't cooperate? Your opponent's job is to do the exact opposite of cooperating with you!

Learn common ideas and themes in the opening you are planning to learn. Then when your opponent deviates, take a good think of why the "main-line" is the main-line, what his idea is, and how to best take advantage of it. 

 Exactly! Sometimes an opponent will play an opening line that is not considered "current" or "in fashion" for this very reason... To get you into an unfamiliar position.  This doesn't necessarily mean that the move is bad, but it does mean that you must think for yourself and not rely on simply memorizing opening moves.

One of the greatest compliments I've been given after a game was that I was "an uncooperative opponent".  This is something that I try to look for in every game - opportunities to do something unexpected that takes the course of the game away from what my opponent is steering for.  Did he make a capture?  Well, then let's look at ALL the choices available instead of just the obvious ones.  I don't always HAVE to recapture his piece... Perhaps I can threaten something else instead.  It's worth a look, and you may just become an uncooperative opponent yourself by doing so!

Good Chess To You!

Brian

A good understanding of the opening principles will serve you well when the opponent deviates from lines you are familar with.

Study them and work on applying them in your games, and see how known opening moves affirm those principles.

Thanks for all your answers. I am sure that any opponent would not want to cooperate. Why would he? So why memorize chess openings, knowing that any good chess opponent will try to thwart your opening plans?

You studied up on Berlin Wall theory due to it being popular at the high level... cute 

2. f4

Somebody please tell me why I should study chess openings.

You don't, just get a playable position out of the opening and destroy your opponents in the middlegame/endgame.

By definition, a chess opening is something people use and memorize in order to reach a short term goal, wether it be a positional advantage, material advantage, etc. The textbook response to whatever particular opening you are using against them is usually the most obvious response, or is the documented best way to respond to your opening-any other move would be inferior. However, you need to truly memorize and understand your opening, and the reason you're playing it, to take advantage of their seemingly fine blunders. When an opponent deviates from the usual response or main line, either they equally understand the opening you are using and know how to counter it, or don't even know what opening it is so they play as if you just played 1e4 or something generic like that. Therefore it is up to you to accordingly respond keeping themes from your opening and openings in general in mind to respond flexibly

Theoretically best moves give you an advantage (or close to it) when playing white, and an equal position (or close to it) when playing black.

Also, sidelines can be chosen to reach middlegames which suite your taste / style / strengths.

you'll probably have to learn how to actually play chess then, rather than just memorizing games. 

Insubordination must be dealt with summarily.

As soon as your opponent deviates from the book line you must quickly stand up, slam your fists on the table and demand they resign. If that doesn't work eat their king.

Indeed. You had better have some opening plans of your own, and not just a rote sequence of moves in your head.

Memorizing will only get you so far. Your opponent can play g4 on move one. Where's your prep now?!?!

               I had a problem with openings once. My doorbell rang. I opened the front door. 7 women came in the BACK door.       GENIOUS I TELL YA

               Here's some serious advice. It comes from the cop show "SOUTHLAND". A policeman asked his training sargent how to make people behave. His answer was;  ASK him, TELL him, MAKE him.

Cote, Pig meant "Scream at him, beat on him, kill him."  Wait, but first he stuffed his grimy hooves into the guy's possessions and took them.  In my town a pig killed a teen on a ding-dong-ditch, chased him down and murdered him in the street because of course the "kid reached for the gun." F'ing swineherd needs put down.  Internal investigation finds no wrong doing.  Standard swineslop.