You haven't started aikido training yet.
Man, what's up with you... you've been taking a stab (no pun intended) at me in 3 threads, in the last 20 minutes.
By all means, then, explain to me how apparently Aikido has a defence for this situation?
Standing close, talking casual, you are not aware an attack is coming, you are relaxed and unaware of danger, you do not know the person has a knife, and the strike comes with "enormous power and fierce speed".
Please, enlighten me as to what technique would allow you to properly defend in this situation.
Are you honestly telling me, that you believe that you, or an average person, and even a "skilled person", training Aikido, would be able to defend in such a situation?
So far, the other replies would disagree with you.
And if you aren't saying that... then what's up with your reply to me?
Average median reaction time, 215ms. Personally I'm all the way up a bit above 300.