most of the material below is now on the main page, in an orgnised fashion; maybe some of it should be on a separate page
dnerra: Maybe we should not teach it to beginners, then? (I think so.)
Bob McGuigan: It is also confusing to weaker players when, as part of an attack, an attaching move is made to make the target stones heavy.
Dieter: (to dnerra) Maybe not, but it is a subject that comes up very naturally. Yesterday at the club evening I kept hammering on the two main principles: connection and liberties. The latter should probably suffice in order to discourage contact plays. Still, there is the diagonal check, which is often as wrong as the contact play. (to Bob) I think that is confusing even beyond beginner level. But such contact plays are rarely made in isolation but most often as a diagonal play.
We all know that the keima and the capping play are the standard moves for attack while the attachment is more of an urgency measure and the one space jump is the basic move for defence. But why is this so?
I believe the capping play is the basic move for attack because that's exactly where the defensive move of the one-point jump would come. And why the latter is the basic defensive move, is adequately explained I believe.
I believe the keima is such a good attacking move in case the focal stones are one space away from each other, which is very frequently so. The keima has a direction (here to the right) and drives towards a strong position.
Now White is faced with a few possibilities:
a) Cut through the keima, but White doesn't want to be cut because she is weak.
b) Play keima herself, but then Black will cut, since he is strong.
c) Leaving the basic defensive move, the one-point jump, but due to the keima it has become a contact play as well:
In isolation, the diagonal approach is answered by a simple block. Now Black has become stronger and is rather weak.
Here, does not really attack the White stones. Up to , he has rather carried out a leaning manoeuver in order to gain strength in the center and for his stones on the right.