I'm going to sketch a couple examples of how inspiration might shape a couple of photographs. This is a follow-on to this post.
Let us suppose that you have a flower, and you want to take a picture of it. How would develop a really good pre-visualization? First you might consciously trundle through some visual ideas. Black and white picture, flower on a white background. Color picture, flower on a black background. Flower in a vase. Flower in my hand. And so on. If you come up with a visual idea that works for you, congratulations, you are done. You might refine the idea mentally, as well as in the studio, but there you are.
What if nothing satisfies?
Notice that you have been going through ideas one after the other. You examine one idea, and discard it or modify it into a new idea. You're going through ideas one by one, at a not very brisk pace. If, after you arrive at an impasse, you relax a bit, a very interesting and powerful cognitive process may occur.
Take a walk, or a shower, or a nap. Evidence suggests that your unconscious mind will continue trying out ideas, but in parallel, many ideas at once bouncing around, banging into one another, combining and recombining. Your mind will pull up an image of the Virgin Mary you saw as a child and bounce that against the image of Mount Doom from the Lord of the Rings Trilogy, and a thousand other possibilities.
Your unconscious mind can sift a much wider range of visual ideas, much more quickly, than your conscious mind can.
If you're lucky, a mental image will emerge, startling and clear, from this dozy chaos, this largely unconscious swirl of ideas and possibilities.
The recognition process is neurologically fascinating, I gather, but I'm not very interested in that. It does seem clear to me that in order to recognize the answer, you must prime those parts of the brain that will say Eureka! You must have consciously thought about the problem with some intensity. Some general notion of what you're after has to be clear, possibly at a very high level. Clean and simple. Dark and moody. Chaotic. Tense.
With the brain's targeting system primed, and a pile of visual material for your unconscious mind to gnaw on, inspiration can strike.
Another example, at the opposite end of some sort of spectrum:
Shooting "street" and shooting portraits have some similar properties. The general idea of what you want exists before you start, but here the moment of inspiration has to occur in real-time. You can produce pretty good portraits, and mediocre street, by conscious thought. For very good work in both areas inspiration is necessary, there's simply no time to consciously think your way through the possibilities and find a truly great image by sheer mental effort. You might find one by accident, but not through effort.
Your mind needs to be in that relaxed state, cutting and trying visual ideas out of sight of the conscious mind (or largely so, at any rate). Through some incompletely understood alchemy, the real world and the unconscious mind will, on rare but happy occasions, converge in an instant and the image will appear in your mind and in the world at the same moment. Click. There must be some process here by which the mental machinery which tests ideas is informed by the observed world. Cartier-Bresson's writing is, at any rate, consistent with this idea. Observing is done intently, pre-visualization is done instinctively.
The intense observation feeds into the unconscious image-tester, driving that engine. The conscious mind oversees, looking for higher level things, looking for ideas and personality in the visual field. Sometimes, inspiration strikes, the image is recognized in an instant, the idea crystallizes, and the shutter snaps.