The exact nature of lucidity is rather difficult to pin down.
We can simply define a lucid dream by saying we are lucid in a dream when we’re in a dream and we know that we’re in a dream.
Yet, the explanation of lucidity itself is somewhat circular: you’re lucid when…you’re lucid.
If we rely on physiological explanations of lucidity, then we can say, “Well, a person is lucid in a dream whenever certain areas of brain related to self-awareness are activated.”
But how do these areas become activated? Sometimes it seems to happen randomly. Sometimes it’s the result of an effort to remember some task, like a reality check, or some other specific action. Or it can be the plain task of remembering to be lucid.
What I would really like to know is: What are the necessary conditions of lucidity?
Lucidity has a few obvious common properties. Two of them are reason and short-term memory. If you’re reasoning fully in a dream, then you’re probably lucid; if your reasoning is impaired, you’re probably non-lucid. Of course, you can reason fairly well in a dream and still never reach the critical mass of consciousness necessary for lucidity. For instance, you might look in a mirror and notice that your hair is too long. You know you had it cut short last week and yet it’s very long. From there, a few things can happen: (1) you conclude you’re wrong about having cut your hair last week; (2) you conclude that your hair has grown very quickly; (3) you conclude that you did definitely cut your hair, and since you’re never seen hair grow so quickly, you must be dreaming.
So we can have some reasoning power in a non-lucid dream, but if there’s a high enough level of reasoning, we could become lucid.
The same goes for short-term, or working, memory. For instance, in a non-lucid dream a DC might change from being a man to a woman. Without our working memory, we don’t notice this, and thus, don’t become conscious of it. With working or short-term memory we might stop and say, “Hey, a few moments ago you were a man and now you’re a woman.” This might to lucidity, and it might not. We might rationalize the change (because of a deficit in reasoning power). Yet, usually, a certain high level of memory in a dream can trigger lucidity. We remember that character X was definitely a man a moment ago and is now a woman—we know we aren’t mistaken. Or we remember that character Y is a deceased person and that we can’t therefore be “really” talking to them.
Anyway, it’s all well and good to say that reasoning and memory are common properties of lucidity, but we aren’t always lucid when our consciousness has these properties in dreams. We must have enough of these things. Although, again, even in highly lucid dreams we still can misremember things. We can certainly know that it’s a dream, and we can have a deep level of control, and yet we might awaken and realize that our father in our dream looked like himself from ten years ago, not himself today, and we didn’t even realize it.
So what really is necessary for lucidity? How can we answer that question without being self-referential or vague? Reason and memory are common to lucidity, but not totally necessary. Some critical level, it seems, of reason and memory are necessary, but at what point do they become so? Obviously, our awareness must change from being passive to being active. We aren’t without self-awareness in a non-lucid dream, but we do lack the quality of self-awareness in which we reflect slowly and intentionally upon our actions, our environment, our thoughts and feelings.
It’s all so slippery, because in some non-lucid dreams we act intentionally. Intentionality is thought of as a property of lucidity, of consciousness, but of course we formulate and carry out intentions in non-lucid dreams. And we sometimes do so with medium levels of reason and memory continuous with our everyday waking lives.
The answer seems to be, to me, in the combination and intensity of intentionality, reason and memory.