That is the point... novice players would like to have all the answers straight away. It doesn't work that way. 
You are rated a little bit below 1 100. If you had almost all of the answers you would be master level.
You will play a game, you will lose, you will look it up with an engine and maybe with a database. You will figure out where was the problem and what was better. Although in 90% of the time the problem will not be the opening. You will play the same line. Perhaps the opponent knows first trick only, because he is probably not a GM himself. Then you will win. Then you will find someone who will know more. Then you will lose.
You will look up the line... rinse repeat.
Of course you will find yourself in trouble every once in a while. That is completely normal. GMs can mess up the opening, so why should we be the exception?
So, opening principles will get you through most of the time but of course that you will fail every now and then. It is understandable.
For instance, I am playing the sicilian. In a year I faced wing gambit once. I ended up not taking the pawn (I think I played b6) and I won the game if I am not mistaken. I saw that it is the best to take and continue the game developing and didn't really look up further. I could have looked up the entire line and multiple options but what would I gain from that? I faced it once... it is just not practical to memorize million different lines that I might face... sometimes.
I know I'm supposed to learn opening principles, not openings . . . but
As for the first example. Of course that you should take the pawn. That is the basic Sicilian stuff. The point of c5 is to challenge that square. He is playing Smith Morra gambit. If he offers another pawn, you could memorize a lot or you can play d3 declining the gambit. Let me show you:
Now for the example where you shouldn't take d4 pawn in the sicilian:
Thank you very much, nklristic. A few things: a) I'm still learning the basic theory behind what the Sicilian is all about. I'm forcing myself to play it, even though I don't really know what I'm doing yet. (A book is on the way! ;-) b) I'm a somewhat stronger player than my rating indicates -- it's just that (as I mentioned) I'm forcing myself to play only Sicilian as black, and 1 d4 as white, because I don't t know much about them and I want to learn -- and also because I really s*ck at rapid chess. In *almost* all of my games, I do pretty well in the opening relying mostly on principles (unless -- as in the Smith-Morra game, I'm thrown a total curveball). I often having a lead for 8, 10, sometimes 15 moves . . . but then I just blunder. I just can't think that fast (yes, I know, I should play slower games!).
In any event, I'm embarking on learning to see tactics better -- which is the subject of my next post later this morning.
In any event, I do appreciate your thumbnail analysis above. That helps. And I like your personal example of facing Sicilian wing gambit and your lesson learned: "it's rare, I'm not going to face it, so all I'll memorize is "take the b-pawn!")
Thanks!
Yeah, take the b pawn. And after I face it again and we go further along, I will look it up again.
Of course I can now think about making some pgn files on the openings I play, for a few moves, nothing major. But even that is still not really necessary. In most of my games, openings are not the problem either.
I think when people advise beginners to focus on opening principles rather than memorizing openings, they're essentially saying that a beginner's early days/weeks/months are BETTER spent with the former than with the latter. They're not saying that there's no benefit to memorizing openings. Of course a beginner will occasionally get flummoxed by a new opening, but as nklristic said, this happens to everyone at all levels. Studying openings (including obscure gambits) is a luxury that beginners shouldn't waste time on until they have developed strong fundamentals.
Ha! You can say that again -- me, too: "in most of my games, openings are not the problem".
So, I think my gut reaction is correct: the advice for sub-1500 players to "don't learn openings" is just too strong. We should learn at least 2-3 moves of the openings that we play and play against.
I didn't notice this earlier, but there was a terrific thread on just this subject a week or two agao at https://www.chess.com/forum/view/chess-openings/beginners-should-learn-openings
Gambits are easy, take the first pawn but leave the second 😁. On a more constructive note, on Chessable, SmithyQ has a free course called Smithy's Opening Fundamentals which I recommend. It mainly focuses on e4/e5. If you prefer paper, then I've just worked through the first 60 pages of Discovering Chess Openings by John Emms which is all about Opening Principles. I thought it was ok. Its aimed at beginners. I'm going back to basics and revising my opening principles as I intend to start actually learning some proper openings when my rating hits 1600. I've been holding off so I can focus on tactics, endgame and positional.
In my opinion beginners should learn openings - but not by knowing moves, but by knowing ideas. For example, after 1.e4 c5 2.d4, if you know the Sicilian, you should know that the key idea of 1...c5 is to prevent white from getting a nice two-pawn center (e4 and d4).
Therefore, you should almost always take on d4.
Also, e6 was a fine move.
Another situation: you want to play the king's indian, but you are faced with the four pawns attack. Well, if you knew thematic ideas, you'd know to play either ...c5 or ...e5. If it doesn't work, you should go over the game and see if it was because of a tactical reason, or because it was too early/late, etc...
You don't have to know "theory" to play an opening. Against London and 2.Nf3 setups in queens pawn games, I play this (as black):
Opening principles such as "control the center" are too loose to be effective. For example, your move ...Nf6 "controlled" the center but allowed white a dangerous pawn roller: e5 Nd5 c4 Nc7 d5!? with a huge initiative and development and space advantage.
'Learning Openings' is an overloaded term with different meanings. I agree it is helpful for beginners to know the mainlines of a few openings, maybe the first 4 to 8 moves. It's less helpful for beginners to memorize 20 variations 12 moves deep 😁. Its not always clear if people mean the former or latter when they talk about learning openings.
Yeah, that's the Smith Morra gambit. The Sicilian has a lot of theory, and many moves that aren't really natural either.
Studying openings can certainly be useful. It's simply advised against because many players study openings incorrectly, by attempting to memorize without understanding.
If you're able to understand what you're studying, though, then keep doing it. Understanding is king.
'Learning Openings' is an overloaded term with different meanings. I agree it is helpful for beginners to know the mainlines of a few openings, maybe the first 4 to 8 moves. It's less helpful for beginners to memorize 20 variations 12 moves deep 😁. Its not always clear if people mean the former or latter when they talk about learning openings.
No beginner is going to know any opening 20 moves deep but for some reason most people believe that’s their intention when they say "learning openings".
I think the claim is misrepresented. it is not that there is no value to studying openings it is that the pay off for the study time is less than if you are than studying tactics, mates, end games and strategy for most people. also there is a difference between studying openings and getting opening suggestions/ideas. Like watching a video on common replies to c5 is one thing and it is not spending time memorizing 10 moves into a position.
Chess Openings Resources for Beginners and Beyond...
https://www.chess.com/blog/RussBell/openings-resources-for-beginners-and-beyond
All the wise people here tell us that we should learn opening principles, not memorize openings. That makes a lot of sense (in fact I myself made a post about it here, where I describe flying totally blind, but because I understood principles, played a "book" opening for a couple of moves against the King's Indian even though I had zero, zip, nada experience playing against it)
I do not come here to disagree! But I do have a slight problem -- and it's this:
What if somebody plays something at you that you've never seen before (say, a gambit of sorts). It's just too hard to sit there for 3, 5, 10 minutes and figure out: is this a gambit trap? What do I have to watch out for?
My example: I was black, and the first moves were: 1. e4 c5 2. d4
d4? What the heck was that? Am I supposed to take that pawn or not? And if I don't, what am I supposed to play?
See, here's the deal: I *am* beginning to understand opening principles. But in real life they often conflict, and a balancing act must be made. (And sometimes, moves have implications that show up 4 moves later, and I'm not experienced or skilled enough to see four moves down the road in an opening)
In this particular example this was my brain's reaction:
"OK. Slow down. Let's see. If I take the pawn that gives him total control of the opening, and he'll follow with Nc3 and grab the pawn back while moving his knight to the center. OTOH, if I play e6 perhaps that will strengthen my d5 square?"
So, I chose e6 -- (later I learned that everybody either takes the pawn or plays d5). So, he plays Nf3. Ok, I should develop my knights, too, so I play Nf6. I'm a bit worried about his putting a bishop on g5, and I figured Nf6 would contribute towards the center rather than the defensive a6 (a6 is apparently a better move, but I was thinking: I don't have any pieces out yet -- only pawns)
Later I learn that's a bad move, and white makes me pay with e5. So, I gotta move my knight. Obvious candidates are to Nd5 or Ne4, I choose the latter because a perhaps I can exploit something on f3. Stockfish really doesn't like that move.
It seems to me that I do need to memorize 2-3 moves for this thing. I need to at least memorize that I need to play 2...cxd4 or 2...d5. No thinking, just memorize those two moves.
Then I went to the books and read about the Smith-Morra Gambit. And I learned that the whole point of 2. d4 is to reply to 2...cxd4 with 3. c3
Yikes! This position looks very wide open and potentially dangerous (both both players), and if white knows some lines here, it could be devastating to black. Further: same question, does black take another pawn here on the third move? Heck if I know!
So here's my point: it seems to me opening principles, while completely and totally essential, isn't enough. I don't see how it gets you past a gambit -- it seems to me that you need to learn the common easily-made mistake when encountering a gambit or other "off the beaten path" openings. (Another example: I've never played a game, or even looked at, the Scandinavian. If someone were to play that against me, I'm sure there are easily made mistakes that can be made even if someone knows "opening principles" half-way decently).
Thoughts?