wrote:

Of course, most games between class players (2000 ELO) are decided by
middle game and end game play, especially tactics. So there are plenty
of openings like this that a grandmaster would never touch that are
perfectly playable for us amateurs.

And, in this case, the psychological advantage of making your opponent
think you're a total patzer, and that they should be able to refute
your opening, might actually be useful. I've seen many people lose by
overextending their position while trying to refute a theoretically
unsound, yet still playable, opening. I even did it once or twice
myself before I realized that the refutations to bad openings often
involve long term advantages, not necessarily something that can be
immediately attacked.

'Unsound', too, is a relative term. It is extremely rare that a single
inferior move in the opening will lead to a forced loss. Many analysts
like to believe this (e.g., Tarrasch-von Scheve, Leipzig 1894, where 7
.... Ne4 is often blamed as the losing error; this seems far too simple,
while 7 ... Ne4 was perhaps not the best and did allow White opportunity
for long-range plans, Black made further errors which enabled the White
plan to succeed. IMO, the most significant of these was the decision to
exchange the darksquare bishop later, with the amount of emphasis on
darksquare play the White plan had, I think if he had retained this B he
would have been far better off, and probably had a playable game.) but
it is not at all common that this is the case.


To get back to the opening under analysis - it is true that Black has a
slight advantage (in either the 4 Bc4 or 4 Bb5 variations, Shredder 6.02
shows Black to be about 0.50 pawn units ahead after ...O-O, White's best
next move being 5 Nc3), and that the variation is surely not good enough
against a strong opponent in a tournament (other than the psychological
advantage, and the practical advantage of almost certainly taking the
opponent out of their prepared repertoire into lines where they must use
their time rather than be able to move quickly by the book, thus
increasing the chance of time pressure later).

But to prove it unsound, Black has to find a win. In fact, the
psychological advantage is increased even further by this, because the
onus of proof is fully on Black. He is a pawn down, and has only some
extra time to show for it as yet. To convert this advantage into a win,
he has to find an overwhelming attack based on it. In fact, to even
draw, he needs to recover his pawn before the bare endgame. Even more
than the Lopez Exchange, if we strip down to the Pawn skeleton this
position is hopeless for Black (it gives about a +2.60 evaluation in
White's favor).

White, on the other hand, for his part, need merely find a successful
defense to whatever Black may throw at him (and perhaps find an
opportunity to attack, if Black leaves an opening).

Note also that the shorter the time control, the greater the advantages
accruing to White. As TCs have shortened over time (from sitzfleisch to
30/120 to 40/120 to slightly faster modern FIDE controls, and of course
the popularity of rapid and blitz - this is even more true in online
chess as well, where players wanting slower TCs are even in the minority
compared to blitzers, and indeed on ICC the blitz rating is the
'default' rating displayed in the player list if not otherwise specified
....)



Another interesting situation when it comes to 'unsound' play occurs
mainly against computers (and mostly lower level human players that
overvalue material advantages). This is the sacrifice, usually of a
piece, in the opening for a positional advantage that is probably
insufficient, though not insignificant. This tends to disrupt computer
evaluations highly, as the computer will generally consider the
long-term advantages of the extra piece as most significant when
choosing moves, even though what is truly most important at the moment
is the opponent's temporary, but often very great positional advantage.

The most celebrated example of this is probably the Muller-Schultz
Gambit, also known as the Halloween Gambit in the Four Knights, which is
initiated by 4 Nxe5. Even against humans, there is some considerable
practical advantage to this move - there is the usual psychological and
preparation consideration accruing to an unexpected opening, and
moreover, the psychological advantage that Black probably expected a
calm, slow, probably drawish game (hence why he chose the Four Knights
to begin with), and is now thrown into a sharp tactical one.

I finish this post with an example from a computer vs. computer blitz
thematic I once ran, as to how quickly even a strong computer Black can
fold in the Muller-Schultz:


Amyan 1.54 - Crafty 18.15 [C47]
(Ca. 2002-2003)

1.e4 e5 2.Nc3 Nc6 3.Nf3 Nf6 4.Nxe5 Nxe5 5.d4 Nc6 6.e5 Ng8 7.Bb5 Nge7
8.0-0 Nf5 9.d5 Ncd4 10.Bc4 h5 11.Ne4 a6 12.c3 Nb5 13.Re1 Na7 14.d6 Be7
15.Qf3 0-0 16.Qxf5 cxd6 17.exd6 Nc6 18.Qxh5 1-0