Kikashi probe discussion
What is the distinction between a kikashi and a probe?
Charles Something like the difference between a paratrooper and a spy?
Is this to say that a stone played as a probe is generally subsequently discarded whereas a kikashi may later be developed?
Charles Well, no. A probe tries to get information; so that you can make a better plan. A kikashi tries to 'force' the opponent to reply; the timing should be good, normally before the big battle starts.
Notochord My understanding: A kikashi is a move that is seen as having generally 1 response, which is (when the kikashi 'works') sente. A kikashi is a move that you can throw in whenever you want (within limits) to get an auxiliary exchange that (may) help directly with doing whatever you are trying to do. You usually expend some degree of aji that existed before the weakness or what have you was defended in exchange for something concrete that is helpful in a context-dependent manner, such as reducing white's liberties or getting a stone in a particular place. Its generally played against something weak, and works to help something 'nearby', in a tactical sense.
A probe, as charles said, looks for information, but maybe in a general sense than by the dictionary. It is a move generally played where your opponent is strong (in his area of influence, more accurately), and is a move that has many possible responses. It removes some of your aji, yes, but what it tries to do is force your opponent to make a specific decision, collapsing some of his own aji, and by making a direct decision, causing one of many of your (miai-ish) large scale strategic possibilities to be better than usually A schematic example of what a probe does: say you have strategic choice A (somewhat distant: a reducing move against some side) and choice B(a direct invasion along the side), which are both kindof mutually exclusive (invasion makes reduction pointless, and the response against the reduction secures the side). You have a probe play (some tsuki against a corner stone, for example) with two choices of response for your opponent: 1 (swallow the stone, let it live for a few points, and take big outside influence) and 2 (bar it from the corner, and try to kill it along the side). Say the exchange of your probe for 1 helps choice A (you get territory, your side invasion wasn't too good anyway, so your opponent protects what's already 'his' while you take corner points from him) and probe for 2 helps B (contributing to your side aji, or otherwise directly helping a potential invader). If you play A before the probe, you can't get the help of 1, since if you tried playing that probe after, he'd play 2. B similarly can't get the help of 2 when you get around to playing the probe. However, if you play the probe first, you can always pick A or B after to make it so that your opponent effectively made the wrong choice, thus improving the strength of your strategic action.
To summarize: Kikashi look for direct local gain from a definite (no choices) tactical exchange. Probes look for larger scale, global gain by an indefinite(your opponent has many choices of response) exchange, allowing you to make the plan that you would choose to each response synergize better with whatever choice (of many) you forced your opponent to make beforehand. It makes it so that your opponent's choice is made with less available information, and yours with more.
It seems I've gone on a bit, and sort of off the topic of this page. Feel free to edit this out or move it or clip it down to size in the near future.
Alex: Here's my take on it.
A kikashi is a move that the opponent must answer (usually in a definite way, but occasionally there are multiple options to accomplish the same goal, such as connection) now, but might ignore at some other time, such as in the middle of a fight. Furthermore, for a move to be kikashi, it must clearly gain more than the opponent's response does.
A probe is a move that will probably be answered regardless of whether it is played now or in the future, but can be answered in several possible ways that all have different meanings (e.g. choosing between territory and influence). If played later, the opponent may know more definitely which of the answers is best for the whole board situation, so by playing it earlier, you force him to make the decision on less information. In contrast to kikashi, a probe doesn't necessarily have to lead to a local gain - indeed, it could even lose a small amount. The value gained from the probe is in restricting your opponent's later options by forcing him to commit to one course of action immediately.