Life In 19x19

A pattern that I don't understand from "crosscut workshop" of Richard Hunter.

Starting position is the following:

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . 1 X . . . . . , . .
$$ | . . 2 3 . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .[/go]

The book suggests the following pattern:

Click Here To Show Diagram Code

[go]$$Bc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . a . . . . . . . . .
$$ | . . b . . . . . . . . .
$$ | . . . 4 . 5 . . . . . .
$$ | . . 2 . . . . . . . . .
$$ | . . O X 3 . . . . , . .
$$ | . . X O . . . . . . . .
$$ | . . 1 . . . . . . . . .
$$ | . . . . . . . . . . . .[/go]

The purpose of Black 1 is given as driving white into blacks thickness above, which is understanable.

But I don't understand white 4. Why not something like a or b, which would make a base? Apparently white does not want to give up the two stones on the third line (therefore does not play lightly), but if the aim is escaping into the center isn't 4 too slow for that?

Could you suggest reasonable continuations if not too complicated?

Thanks in advance!

I think then black could cap white and then play the vital point to kill.

Thanks LiKao. But I still don't understand the meaning of white 4. Where would black cap? Where is the vital point? Is the purpose white 4 making eye shape?
This is not at all obvious to me.

Anyway it seems that nobody else is interested in this question. Maybe I am missing something severely obvious. The book is also silent about that.
I thought it could be a meaningful shape study, but apparently it isn't.

entropi wrote:A pattern that I don't understand from "crosscut workshop" of Richard Hunter.

Starting position is the following:

$$Wc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . 1 X . . . . . , . .
$$ | . . 2 3 . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .

Click Here To Show Diagram Code

[go]$$Wc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . 1 X . . . . . , . .
$$ | . . 2 3 . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .[/go]

The book suggests the following pattern:

$$Bc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . a . . . . . . . . .
$$ | . . b . . . . . . . . .
$$ | . . . 4 . 5 . . . . . .
$$ | . . 2 . . . . . . . . .
$$ | . . O X 3 . . . . , . .
$$ | . . X O . . . . . . . .
$$ | . . 1 . . . . . . . . .
$$ | . . . . . . . . . . . .

Click Here To Show Diagram Code

[go]$$Bc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . a . . . . . . . . .
$$ | . . b . . . . . . . . .
$$ | . . . 4 . 5 . . . . . .
$$ | . . 2 . . . . . . . . .
$$ | . . O X 3 . . . . , . .
$$ | . . X O . . . . . . . .
$$ | . . 1 . . . . . . . . .
$$ | . . . . . . . . . . . .[/go]

The purpose of Black 1 is given as driving white into blacks thickness above, which is understanable.

But I don't understand white 4. Why not something like a or b, which would make a base? Apparently white does not want to give up the two stones on the third line (therefore does not play lightly), but if the aim is escaping into the center isn't 4 too slow for that?

Could you suggest reasonable continuations if not too complicated?

Thanks in advance!

follows the proverb not to approach strong stones. It threatens to jump out to 5. OTOH, if White extends to "a" or "b", Black can play at 4.

Thanks Bill.

But sooner or later white will inevitably approach strong stones, since white cannot escape into the center.

threatens to jump, but it is obvious that black will immediately take that point with

Then the meaning of is making potential eye shape in sente. Is it correct?

Would white still play it (thus giving black for free), if he knew that white can anyway live just by extending to a or b? OK, black can play at 4 but would it kill white?

That's probably what confuses me. I fail to perceive as making good shape for life. Anyway, a fundamental(?) principle to think about for me... Thanks

Click Here To Show Diagram Code

[go]$$Bc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . a . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . 4 . 5 . . . . . .
$$ | . . 2 . . b . . . . . .
$$ | . . O X 3 . . . . , . .
$$ | . . X O . . . . . . . .
$$ | . . 1 . . . . . . . . .
$$ | . . . . . . . . . . . .[/go]

I think White now wants "a", but White's shape is good. Don't underestimate the aji has created at "b".

entropi wrote:Thanks Bill.

But sooner or later white will inevitably approach strong stones, since white cannot escape into the center.

Better sooner, or better later?

threatens to jump, but it is obvious that black will immediately take that point with

Then the meaning of is making potential eye shape in sente. Is it correct?

What is the first rule of making life? Enlarge your potential eye-space.

4 is a key point for both players. If White plays there first, it will be sente. OTOH, if White simply extends on the third line and allows Black to play there first, it will also be sente -- or maybe worse. Which does White prefer?

Click Here To Show Diagram Code

[go]$$Bc
$$ | . . X X . X . . . , . .
$$ | . . . . . . . . . . . .
$$ | . . 7 . . . . . . . . .
$$ | . . 5 6 . . . . . . . .
$$ | . . . 4 . 8 . . . . . .
$$ | . . 2 . . . . . . . . .
$$ | . . O X 3 . . . . , . .
$$ | . . X O . . . . . . . .
$$ | . . 1 . . . . . . . . .
$$ | . . . . . . . . . . . .[/go]

Doesn't look so good for b now, eh?