Problem life and death #21 beginner, on Hactar Go. After move 5, it says solved, but isn't it just seki? I understand, that's a better outcome than dying - is seki usually considered life in such problems? Also, is my evaluation right, is this seki?

Black's goal is to live. After he has achieved that goal, as there is no way for white to capture black any more. The fact that black cannot capture those three white stones is not relevant to solving the problem.

So yes, it is seki, and that seki solves the problem.

don't think of seki as "Whoever goes first loses" (as you say in your sgf example).

instead, think of seki as dual life -- both live.

Also, in your example, is unnecessary. Black can't capture white's stones even with that liberty, because white can throw in to the center of the three stones and reduce black to one eye.

Seki is considered life but inferior to unconditional life and usually better than a ko for life if I remember correctly (unless you're given a specific thing to find, e.g. a two stage ko for life or whatever).

Yes, unless you need to win the ko to win the game.

Sorry, I was unclear. I meant in the context of tsumego, normally a seki solution is wrong if there exists an unconditional life solution and so on.

Seki IS unconditional life.

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Still officially AGA 5d but I play so irregularly these days that I am probably only 3d or 4d over the board (but hopefully still 5d in terms of knowledge, theory and the ability to contribute).

You are correct, I should have said independent life? (I've always had trouble considering seki as unconditional as I've always thought of unconditional implying an ability to tenuki by the defending player, at least once regardless of who begins the sequence. I see that I'm incorrect though.)

Yeah, there's not a good English term for life without seki, as far as I'm aware. It would be convenient if there were, and would probably help avoid potential confusion with "unconditional life".

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Occupy Babel!

Well, another term for seki is mutual life. Independent life makes an obvious contrast.

As for unconditional life, it means something different in the context of tsumego (life without winning a ko) and in the context of static determination of life and death (life without placing a stone). Seki is unconditional life in the first sense, but not in the second sense. For the second sense I have suggested invulnerable or immortal, Charles Matthews has suggested safe.

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The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

"Whoever goes first loses" is slightly inaccurate for this seki. "Whoever plays first loses" is accurate, as long as we mean playing a stone in the seki. That is not true for all seki, however, so xed_over is right.

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The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Depending on the rules used a life-in-seki position might be inferior to a two-eye life because the two-eye life gives territory while points in a seki are not counted (Japanese rules)

It's a bit off topic but I think it is worth mentioning that one way of living may be preferable to another because of subsequent endgame plays.

Independent of the rules a life in seki position is inferior because it also depends on none of the surrounding groups dying.

In fact, if we take the word "unconditional" literally, seki is not unconditional life because it is only alive on the condition that none of the outside groups die.

Conversely, there are positions where both seki and independent life are possible, but seki gives you more points (independent life requires a sacrifice of some sort).

If it is a small seki and you have a high value ko fight where you could win if you sacrifice your seki, you probably would.

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