Why is theory so important in the sicilian?

I don't understand why in many posts I see that say for example that a najdorf sicilian requires alot of theory or else you will get destroyed. I don't understand this. I don't play the sicilian, my concern is beating it with white. Isn't it enough to know that I want to launch a kingside attack with my f and or g pawns and pieces while preventing black from getting counterplay? honestly I haven't played in many main line sicilian games though.

If theres any opening that needs no theory, I'll play it.

WOOOOT 2 hrs a week more time

I play the Sveshnikov Sicilian and it's very tough. Before every tournament game, if I'm black, I take out my Sveshnikov book and study for maybe 10 minutes. There are so many lines in the Sicilian, and like tonydal said they're very sharp. I usually have trouble playing online blitz with someone who knows what they're doing against my Sicilian and end up getting run over in the center.

In the sicilian many positions are unbalanced and dynamic, and it's difficult to assess them correctly over the board without knowing some thematic ideas, as calculating them "live" is often very difficult for most players.

That s the poisened pawn variation of the Najdorf right?Black must play ultra sharp this variation.

One other point about positions in most mainline Sicilians not mentioned is that many of the moves are rather counterintuitive for both sides. Knowing theory really helps since trying to reproduce the positions or moves would be extremely difficult and/or time consuming if not impossible.

This is why I don't play Sicilian too much.  I don't want to study too much, so I play offbeat openings, so my opponents cannot throw so many traps at me that they know about.  I do better with offbeat openings.

ya that is posioned pawn varition black is peferctly ok kasparov and anand have played it as black

does the Bb5 variation also require alot of theory?

you know when you play maybe 1.e4 e5? then maybe you move 2.Nf3 and he thinks " oh i must protect pawn with 2...Nc6 and then you throw out 3.Bb5 pinning knight threatening to take pawn again and so on? you can play like "oh if he does that then i do that and if he does that then i do that. you can get a long way by simply understanding whats going on here without to much theori.

well in the sicilian you cant do that because its a race on each side of the board and the first player to the goal wins. when you see who is winning the race its most likely at the end of the race and its probably to late to do anything about it so you pretty much need to know it by doing your homework in the sicilian. in addition you must check all the time if the center can be blown open and who benefits from it on every move. complicated stuff to get right over the board sometimes. i hope this helps:)

And then we sit down to play the game and I play 1.d4

The only thing I don't like about the Sicilian is that many people I play against (my average opponent's rating is 1460) don't play 3.d4 - instead they play 3.d3 or 3.Bc4 4.d3 . This means I don't get to play many proper Sicilians and when I do, my opponent knows the game better than me.

What's the best way to "punish" people who don't play 3. d4? (assuming the alternatives are bad moves)

I think a better way of characterizing moves other than 3.d4 would be "not a serious try for an advantage" -- talking about 3.d3 or 3.Bc4 with plan of 4.d3.

I think you should just play to control the center, the usual stuff. If Bc4, typically you would play e6, and then if d3, you can play a6 where they'll probably play a4. You can play a black setup similar to the Closed Sicilian, where you make these moves:

c5, Nc6, d6, e6, Nge7 g6, Bg7

I know that sicilian players would hate me to say it, but are the open sicilians truly sound? It gets very complicated, but ultimately I think white will be ahead in the race. On fritz it always says something like .7 when I play through many book moves and like in the dragon when white plays the yugoslav attack I'm sure he has a quicker attack and black will probably absolutely need to find the concrete solutions to these problems by studying the moves but even then if white plays his correct moves I think his attack comes first. And also the najdorf isn't favored by the computer either and it does look as if black sure is wasting alot of time. Everyone calls the sicilian as a sound way to fight for the initiative but can he really get equal chances when white has all of those pieces out? Of course white will probably not play the best moves but the fact that white can get some very dangerous threats at least shows how risky a sicilian can be for black. The up side is just that if white makes a mistake black has his counterplay, but you can't just hope for that and expect to win all the time! The sicilian is dangerous for both sides (open variaiton) but I can see why the computer prefers white's position so much. This lack of solidity if white plays correctly is why a computer thinks the best strategy with black is to hold on for the draw with ...e5 and safely punish a potential mistake from white but not as much. I know people make many mistakes, but seriously does it have to be favored this much by even GM's?

That's what I usually play - followed up with a6, b5. I guess I'll keep it up then, thanks!

Yeah - extreme sharpness (in some lines - not all of them) combined with very rich positions (I mean, they're extremely sharp, have been worked on for decades and still they're not worked out entirely) combined with popularity.

But don't forget that this holds only for some lines - Bg5 and Be3 Najdorfs, Yugoslav attack Dragons, that sort of thing. If black plays the Accelerated Dragon, theory is much less important. Similarly, white could play quiet Be2 or g3 systems, which are still dangerous for black, but need far less theory for the white player.

So in that light, the popularity of the antis (that give black easy equality) is a bit odd. On the other hand, currently I play 2.c3 myself, so who am I to talk :-)

play the sicilian with someone weaker than yourself or play the french with someone equal or stronger

     Because there are so many sharp unbalanced positions that arise. In many openings making a second-best move may result in uncomfortable positions or slight inequality, the Sicilian is one of the openings with enough pitfalls that a second-best can lead to disaster.

Why the hell are you bumping a thread from 12 years ago? Make a new thread on the subject if you want to. 

Sicilian is combative , filled with so many variations, and the best lines, have good objective evaluation. This means it has been played and analyzed to death.

Since the lines have been so analyzed, even weak players can play very strong chess for quite some time, by following theory but the same goes for white side . As a result, theory developed way more on the sicilian than most other openings. It's reputation also means its one of the most respected and studied lines, and this perpetuates new devotees. 

To answer your question though, for the black side, sicilian positions are very subtle and its virtually impossible to calculate your way through all the positional consideration and subtle move order differences, if you just play on general ideas you will soon find yourself in an inferior position and in some lines just get wiped out to preparation. For the white side, the best tries for advantage lie on the labyrinth lines of the open sicilian, but you must be ready for so many variations to come out ahead. Natural play as white can get black to equalize easily or worse

So basically, a combination of complicated lines and immense popularity