Another point regarding this narration pertaining to the use of the word, "delirious". The root of the Arabic word (used in the narration) means, "to desert, depart, separate, forsake, leave, renounce, abandon" etc. What is understood by it is that the people were asking if the Prophet's (saw) consciousness had deserted, or departed from, or separated from, him. In plain English, it was an inquiry to find out if the Prophet (saw) was still conscious. The proof for it is in the text of the hadith. Allow me to quote two with different wordings.
…The ailment of Allah’s Apostle became worse (on Thursday) and he said, “Fetch me something so that I may write to you something after which you will never go astray.” The people (present there) differed in this matter, and it was not right to differ before a prophet. Some said, “What is wrong with him? (Do you think) he is delirious (seriously ill)? Ask him (to understand his state).” (Sahih Bukhari, Volume 5, Book 59, Number 716)
The illness of Allah’s Messenger (may peace be upon him) took a serious turn (on Thursday), and he said: “Come to me, so that I should write for you a document that you may not go astray after me.” They (the Companions around him) disputed, and it is not right to dispute in the presence of the Apostle. They said: “How is (Allah’s Apostle)? Has he lost his consciousness? Try to learn from him (this point).” (Sahih Muslim, Book 013, Number 4014)
Leaving aside that which are in brackets and ignoring the phrase, "Has he lost consciousness" (found in Sahih Muslim), I want to focus on "Ask him" and "Try to learn from him".
If, naudhubillah, as the Shias say, the Companions (ra) meant that the Prophet (saw) had become "delirious" (literally) and had gone crazy, naudhubillah, would they ask the Prophet (saw) or try to find out from him? Do you ask a crazy man if he is crazy? What is going to be his response? It will be, "no, I am not". Is the testimony of a delirious (crazy) person admissible in court? Therefore, this is the incorrect understanding of the hadith; a wishful thinking on the part of the Shias.
The correct understanding, as per the two statements of the Companions (ra) "ask him" and "try to learn from him", is that they were trying to find out if the Prophet (saw) had become unconscious. How do you verify if a person is still conscious? You "ask him" if he can hear you (etc) or you "try to learn from him" by shaking him gently, etc.