How can you deliver checkmate with a king?

It could be the bishop or the rook, but there's no clear answer because you provided no indication of what the last move was.

That is not the right answer as I analyzed in my previous post (I did answer the question). The rook is giving check in the diagram but it is a state, not an action. And it is the state after the move that checked black and which could have been delivered by either the rook or the bishop. So it is perfectly possible that the rook is giving check now but the bishop delivered that check on the last move! A move was played which changed the state as moves always do! In mathematics "a move" is defined as the total change in system state during one turn of a player.

Read the rest of my last post to get an answer to the next 10 questions lfPatriotGames will invent!

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Look-ahead and Threats.

The question is why anyone would be confused on these issues. I am pretty sure of the answer. The check and checkmate states we are discussing are not ordinary states like "my face is blue" or "the weather is hot" - they are "look-ahead" states. Check and checkmate have implied future actions in them in particular "a piece attacks a king" which translates in the mind as "my piece delivers the threat of capturing the king". Which is true in a way, only it's not how we define delivery of states in chess. All states are delivered by moves in a uniform process and the "king capture threat" is treated the same as a "queen capture threat" or "a threat to destroy the opponents castling right". Threats only constitute future actions and plans but are not deliveries.

None of this discussion would have occurred if the rules had abolished check and checkmate and allowed "capturing the king". Delivery of "king capture" is plain to see and not different from "capturing a queen" or anything.

With the current rules the look-ahead bits generate issues in the resolution of formal queries as we already knew in fairy chess for a long time. For instance, many fairy types have a potential for two types of checkmate - orthodox and fairy - dependent on whether or not you virtually apply the fairy rules up to the king capture!

The checkmate with a king, you need to do a discovery attack by moving the king resulting in a checkmate

Just an example this position is impossible to get

Be careful what you write. That's how this 90-posts thread started!

Lucena might object to this. Here is the position from his famous book

Mate in 4

yeah, that'll work

but I don't think you will find this situation often in a game :-)

OK, so from that diagram you just don't know, right? So lets go back even further. Is the king in check? The possible answers are:

Yes

Maybe

No

Seven

Tuna Casserole

I would be willing to bet a thousand dollars both this question, and the previous one have a definite answer, and it's not "there is no clear answer", the answer is crystal clear. It seems very likely you just don't want to say the obvious answer because it points to which piece is checking the king. It's ok.

How can you deliver checkmate with a king?

WITH CASH. cash is king.

As has been said thousands of times, check is simply an attack on the king, while checkmate refers to an entire position. If you know 63 of the 64 squares, you can't be sure if it's checkmate or not because even though the king is in check and he can't run, what if something on the 64'th square can capture the checking piece?

With this newfound knowledge that a checkmate is an entire position, hopefully you'll find it logical that the piece that changes the position into a checkmate is the piece that takes the action of checkmating the enemy king.

I bet @lfPatriotGames is a flat-earther.

Chess players are already flat-boarders. Flat earth is a tiny step

If moving your king results in the opponent being checkmated by that action, aka discovered check, than you get Killer King.

No disagreement there. So in this position, which piece is checkmating the king? But first I guess we have to ask if the king is even in check. If so, which piece is checking the king. And then if it's checkmate. And lastly, which piece is checkmating the king. Not according to philosophy or "folklore". But the rules of chess.

Apparently it's a very difficult chess puzzle.

If you payed any attention at all to what I wrote (and please read carefully here), checkmate refers to an entire position, not simply an attack on a king, that is a check.

So if a checkmate is an entire position, the piece that moves and, therefore, changes the position into checkmate, is the piece that checkmates. Apparently the definition of the word position is very difficult to understand.

The rules of chess state: "The purpose of the game is to checkmate the opponent's king. This happens when the king is put into check and cannot get out of check."[1]

Which piece caused the king to be put into check and cannot get out of check, in the position below?

Is it the bishop? The rook? The king? The knight? Or the queen on the other side of the tournament hall?

Apparently understanding which piece is moving is more complicated than I thought.