Half knowledge is very dangerous...  

I'm sorry your another friend doesn't trust your half knowledge friend anymore. I don't have any half knowledge friend. I have full knowledge friend. Maybe another is three fourths knowledged friend but none of them are half.

I agree with you that when we have half knowledge, don't talk to much. You know, many effect can be happen. As your friend's experience that he given wrong answer or if it about experiment, it will be big mistake.

A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.

Alexander Pope

all the best urban

your friend leaned on his own understanding...over confidnent but "half-cooked".
people like that are mushrooming around.

I do have some of these type friends. But i know they have only half knowledge so i dont trust them. But in fact they are good friends and if they dont know then they will say i dont know. But they are dangerous if they teaches us wrong answers.

Half knowledge is like you know something yet not completely sure about that full knowledge. I mean you don't know the whole story and you only know the part and pieces. And if you share it with someone there's a chance that the person you give the half knowledge into will make some mistake and ultimately will blame you.

In my case I would never share a half knowledge to anybody or even a close friend of mine because I might given something dangerous information. And some information can never be retrieve and might be fatal.