I think it was Arthur Ellison who compared the subconscious to an idiot savant. His point was that the subconscious has vast abilities but limited intelligence. Basically, the subconscious is like a rather stupid child who believes whatever you tell him. This is true even if you don't consciously believe what you're saying.
For instance, one way I motivate myself to write is to tell myself that I have to do just two paragraphs. Two paragraphs, that's all. Hardly anything. A postcard might be longer than that. No excuse not to do two little paragraphs.
Now, consciously I know that I am playing a trick on myself. I know that my real intention is to write more than two paragraphs. I know that once I have written two paragraphs, I will probably be on enough of a roll to keep going and write two or three pages. So I know I am lying when I promise that my output will be only two paragraphs, nothing more.
Nevertheless, the trick works. I do feel motivated, do start writing. My subconscious buys it - every time.
The same approach can have negative consequences, too. Suppose you try to motivate yourself by saying, "This work I've done just isn't good enough." Consciously you're trying to get yourself to do better. But your subconscious does not grasp such subtleties. It hears, "This isn't good enough," and concludes, "It's no good." Then it makes you feel depressed. Instead of getting pumped up, you feel deflated - all because your subconscious is so literal-minded.
If your subconscious is dumb in some ways, it has prodigious talents in other areas. It's well known that if you can't remember a certain fact, the best thing to do is tell your subconscious to retrieve it, and then consciously forget all about it. In a short time the answer will come to you - delivered by your subconscious, which has just sorted through millions of bits of data to find the one item you requested.
The real power of the subconscious is most apparent in cases of hypnotism. I think that when a person is deeply hypnotized, he basically allows the hypnotist's consciousness to substitute for his own. In other words, the hypnotized person's consciousness is shut down, and his subconscious is responding directly to the hypnotist's suggestions or commands . That's why hypnotism can be so powerful. If the hypnotist tells a person that his arm is rigid and immovable, then almost no amount of force will move the arm. If the hypnotist says that the arm is weak and helpless, even the slightest pressure will move it.
The subconscious, under hypnosis, can even persuade people they're feeling no pain during invasive surgery, without anesthesia. It really is an idiot savant - dumb and gullible, yet awesomely effective.
Are people who commune with "spirit guides" actually in touch with their own subconscious? Or do their guides speak through the subconscious simply because they encounter less interference that way? Or is the subconscious itself part of a larger spirit world that we enter only in meditation and dreams?
Can the subconscious alter physical reality? If what we call reality is, in some respects, a projection of the mind, then presumably altering our subconscious beliefs will alter reality. But maybe reality is a shared projection of many different consciousnesses, in which case changing our own subconscious may not have much of an effect on the whole. Or maybe reality is not a projection of the mind at all. Maybe the dualists are right, and there is a sharp division between mind and matter.
I don't know. I'll have to leave these questions with my subconscious and see what it comes up with.