I learnt that obnosis means "observing the obvious", but with an n thrown in. The link above describes the training procedure for learning how to obnose. The first phase involves a bit of unlearning. People are encouraged to say what they can see and discouraged from making any kind of assumptions. So we have this gem:
The student realises what is expected of him; that he is to observe only what is immediately in front of him, without making any kind of deduction whatsoever. Now, let's try and spot where this gets into trouble.
A student starts to catch on and says, “Well, I can really see he’s got ears.”
-“All right, but from where you’re sitting can you see both ears right now as you’re looking at him?”
-“Okay. What do you see?”
-“I see he’s got a left ear.”
The goal of such drilling is to get a student to the point where he can look at another person, or an object, and see exactly what is there. Not a deduction of what might be there from what he does see there. Just what is there, visible and plain to the eye. It’s so simple, it hurts.
You can get a good tip on chronic tone from what a person does with his eyes. At apathy, he will give the appearance of looking fixedly, for minutes on end, at a particular object. The only thing is, he doesn’t see it. He isn’t aware of the object at all. If you dropped a bag over his head, the focus of his eyes would probably remain the same.
That's right. The second phase in this training, having been taught to discard any kind of assumptions in what we observe, is to then learn a whole new set of assumptions; assumptions based on the Tone Scale1, itself an arbitrary hierarchy of mood and behaviour.
It's often been said that Scientology seeks to destroy a person's existing mental tool set and replace it with its own; that Hubbard tears down someone's identity and rebuilds it in his own image. This pattern is clearly demonstrated in the learning process of obnosis. We have a range of learned assumptions; Scientology gets you to unlearn them so that you can replace them with Hubbard's assumptions - obnosis has nothing to do with "observing the obvious" and everything to do with sticking the tone scale between the subject and the world at large.
1 The Beacon revels in the fact that the Tone Scale puts "sympathy" in at 0.9 and "no sympathy" in at 1.2; low tones both! And let's not forget that LRH believed everyone below 2.0 on the Tone Scale ought not have any civil rights.