I have wondered about the difference between a mental image and a "real image"; the difference between an object you are looking at and an object you are thinking of. Think of the colour red. Apparently, this "colour" is not quite the same as one you would see, yet we can make a correlation. We can think of a red ball, but apparently we can conceive of nothing but a "red ball", with nothing else, in the middle of nowhere. We have never seen anything quite like it, yet we can think about it. You can't touch an object that is hot and cold at the same time, but you can touch a hot object and think of cold. You can think of what a person looks like, and still be well aware that the person is not anywhere within sight. You can even have a song ringing in your mind while listening to a lecture.

Apparently, the realm of thought and sense are separate; they seem be independent of each other at any given point in time, and we are aware of it. No matter how one can vividly imagine and fantasize, he is still well aware that the images are not the same as what he would see with his eyes; one can have an imaginary discussion within his mind during an examination and he can be quite sure that he is not listening to something that others can hear. Best of all, one can mentally curse someone in the person's face with a smile, and be certain that the person would not hear it.

My dreams are vivid and uncontrollable. The strange thing is that as I recall from the transition from thought to dream, there is no defining point when things start to appear as sense instead of thought. Perhaps, the ability to distinguish between sense and thought is diminishing as I perceive less sense data. When I close my eyes, I can make myself see my eyelids if I want; I can make myself feel the cloth on a particular part of my body; I can feel myself breathe, but after a while, when thoughts start flooding my mind, I don't sense them anymore. At a reduced level of "consciousness", the distinction between thought and sense become less clear.

But I might have just been taking this ability to distinguish between thought and sense for granted. Apparently, schizophrenic people can't.