Life and Death Basics — Eye Space, Vital Points and False Eyes

Sooner or later, while solving life-and-death problems, you hit a moment where you look at the answer and still can't see why it is the answer. Usually that is because you skipped the idea of eye space. This article explains how to treat life and death as something you calculate, not something you feel.

Intermediate Go · about 9 minutes to read

Life and death comes down to two eyes

To survive, a group needs two separate eyes. With two eyes, the opponent can never fill both at once, so the group can never be captured. That is the only conclusion life and death ever reaches; everything else is the process of working out whether two eyes can be made.

So there are only two kinds of life-and-death problem: living problems, where the surrounded side tries to make two eyes, and killing problems, where the attacker tries to prevent them. The first thing to do with any problem is to check: "Am I trying to live, or trying to kill?"

Eye space — the size of the enclosed area

Eye space is the empty area enclosed inside a group. Nearly every life-and-death judgment comes from the size and shape of that eye space.

Here is the rule of thumb.

• 2 points or fewer — always dead. There simply isn't room for two eyes.
• 3 points — dead if the opponent plays the middle point. If you play first, you live.
• 4 points — depends on the shape. This is where real life and death begins.
• 5 and 6 points — usually alive, but certain shapes are dead.
• 7 points or more — usually alive.

From four points onward, size alone is not enough and you have to look at the shape. That is why it pays to memorize a few basic shapes.

Basic shapes you must know

Straight four (4 points in a line)

Four empty points in a straight row. It is alive. Wherever the opponent plays inside, the remaining space splits and two eyes are left. More precisely, if the opponent plays one of the two inner points, you play the other and get one eye on each side.

Bent four (4 points with a bend)

A four-point space bent into an L shape. This is also alive, for the same reason as the straight four.

Square four (4 points in a square)

A 2×2 square. This one is dead. Whichever point you play, the remaining space does not split; it stays in one piece and gives only one eye. The same four points produce the opposite result, which is why beginners get this wrong more than anything else.

Flower six (6 points)

A six-point space spreading out like petals around one central point. It looks spacious, but it is dead. If the opponent places a stone on the central vital point, the eye space keeps shrinking until it is reduced to a single eye. It is the classic example of why you cannot trust size alone.

Finding the vital point

In life and death, the vital point is the spot where a single move decides life or death. There are a few tricks for finding it.

The center of the eye space

The most common vital point is the middle of the enclosed space. The killer plays the center so the space cannot be split in two; the defender takes that point first to secure the space. The middle of a three-point space and the center of the flower six are both examples. Playing inside the opponent's eye space like this is called a placement.

Points that widen the eye space

If you are trying to live, play in the direction that enlarges your space. In particular, a hane toward the edge that widens the space by even a single point can turn a dead shape into a living one. Conversely, the killer blocks that point first to shrink the eye space.

Cutting points

Even something that looks like an eye stops working as one if the stones around it are cut apart. Cut where the opponent's connection is thin, and territory that looked perfectly safe can collapse.

In real games, checking these three in order catches most vital points: try the center, look for the point that widens or narrows the space, then see if there is anything to cut.

False eyes — eyes that aren't eyes

A false eye looks like an eye but isn't one. Some of the stones around that empty point are in atari or can be cut off, so in the end the opponent can fill it.

Telling them apart is simple. Check whether the stones on every side of the eye (two sides in the corner, three on the edge, four in the center) are safely connected. If even one of them can be captured or cut off, the eye is false.

When a problem's answer says "it clearly has two eyes, but it dies," nine times out of ten there is a false eye. Get into the habit of checking that each eye is real instead of just counting them, and your success rate will rise noticeably.

Seki and ko — neither alive nor dead

Not every life-and-death fight ends in life or death.

Seki

In seki, black and white groups are tangled together so that whoever plays first loses. Neither side has two eyes, but neither can touch the position first, so they coexist as they are. Points inside a seki count as territory for neither player. Stones you thought were dead can sometimes survive in seki, so if your eye space is too small, aiming for seki is an option.

Ko

Many life-and-death fights end in ko. Then the side with more ko threats wins. If unconditional life isn't possible, holding out with a ko is the next best thing. It is not unusual for the answer to a life-and-death problem to be "ko."

How to study life and death efficiently

Life and death is the most honest part of Go. Each problem has one right answer, and you improve exactly as much as you solve. But the wrong method just burns time.

• Many easy problems. Rather than wrestling with a problem for more than five minutes, solve lots of problems you can crack in 30 seconds. Life and death is pattern recognition, so the number of exposures matters.
• Read to the end before checking the answer. Getting only the first move right and moving on teaches you nothing. Play out in your head how the opponent will resist and how you will answer.
• Redo the problems you missed. Solve the same problem again a day later and you'll know whether you really understood it.
• Remember shapes, not answers. Remember "this is a flower six, so the placement in the center," not "the answer to this one is the top left." That is what carries over to other problems.