I must be very bad at explaining myself.
I did not state that it is easy to do aikido against a knife attack - I just said that aikido is constructed to deal with it. Evasive movements instead of blocks, and so on.
I also stressed the probability thing: if you know your aikido well, your odds are better than if you don't. Also - and this is very important - the better the attacker is trained with the knife, the worse odds you have.
On the other hand, if the attacker is not trained with the knife (and that is quite often the case "in the street"), your odds are increased. Not that you want to bet on it with your life, but that's probability at work.
There is no absolute. Just probability. Also for the one with the knife (who can never even be sure of being the only one armed).
Of course fighting is the last option - always, not just when facing a knife, but especially when meeting an armed attacker.
Regarding the "done for" bit, I have observed that most posts stressing the danger of the knife (which is certainly correct to do), give little or no indication of what to do in such a situation, except run away, if possible.
That's what I meant. The overall message on this thread seems to be that if facing a knife, you're done for.
I am glad that I was mistaken. Now, I hope for some tips from the guys who are fully aware of the danger of a knife. What to do when facing it, if not being able to run away?
Again, pardon me for expressing myself so poorly, probably in this post as well. If you do me the generous honor of crediting me with some level of intelligence, you may find it possible to figure out what I might be trying to say.