Modern philosophy began with an interest in consciousness, as Descartes reasoned to the fact of his existence from the act of reasoning itself -- his conscious awareness of thinking. 

 And so did modern psychology.  The 19th-century psychophysicists were interested in the relations between physical stimuli and conscious experiences, and the structuralists sought to analyze conscious experience into its elementary constituents.  William James -- more than Wundt, perhaps, psychology's founding father -- defined psychology as "the science of mental life", whose goal was "the description and explanation of states of consciousness as such".

Even so, psychology -- and, later, cognitive science -- managed to avoid the problem of consciousness for a long time, for a combination of reasons that are either neurotic (e.g., positivistic reserve), strategic (e.g., the piecemeal approach), empirical (e.g., conscious inessentialism) or ideological (e.g., the epiphenomenalist suspicion) in nature.

Nevertheless, the cognitive revolution in psychology brought with it a resurgence of interest in consciousness, in the form of research on attention and short-term memory.  Interest in consciousness was further stimulated by the "rediscovery" of unconscious mental life -- first in the form of automatic mental processes, later in the form of implicit memory in amnesic patients.  More recently, the concept of "theory of mind" has refocused interest on conscious as opposed to unconscious mental states.

How can we achieve a third-person understanding of a phenomenon with a first-person existence?

As Searle puts it:

Once we have decided just to get on with it, it turns out that the scientific problems of consciousness come in three broad categories:

Ever since Descartes, at least, philosophers, psychologists, and other cognitive scientists, to the extent that they have been interested in consciousness at all, have been mostly interested in the mind-body problem, and especially in one particular form of the mind-body problem: establishing the neural correlates of consciousness. 

The first step in solving the mind-body problem is to define consciousness -- for without a satisfactory definition of consciousness, we cannot hope to establish its neural correlates.  (Without such a definition, we literally do not know what we are talking about!)

Of particular interest, I think, is the explicit-implicit distinction, which assumes that memories, percepts, etc., come in two forms: explicit or conscious, and implicit or unconscious.

By directly contrasting explicit (conscious) and implicit (unconscious) expressions of the same mental state, I think we have the best chance of answering the question of the neural correlates of consciousness:

What is the difference that makes for consciousness?

But it's important to remember that there are two mind-body problems, not just one -- namely,

How does the mind affect the body?

This is the hoary question of "free will vs. determinism".  In terms of the mind-body problem, the question is whether our mental states are epiphenomenal after all, or whether they actually have some causal function.

Scientifically, this question gets addressed in two ways:

Again, the explicit-implicit distinction can be a useful vehicle for research:

Again, by directly contrasting explicit (conscious) and implicit (unconscious) expressions of the same mental state, I think we have the best chance of answering the question of the function of consciousness:

What is the difference that consciousness makes?

In the meantime, it's also important to remember that the scientific approach to consciousness ranges far beyond the mind-body problem.

In the first place, it's important to remember that psychology really is the science of mental life, and so many topics within psychology can be approached with an eye toward their implications for consciousness.

So there may be merit in the piecemeal approach to consciousness after all -- but with the difference that psychologists who are interested in consciousness will bear in mind that they're studying conscious perceptual experience -- not simply the processing of information contained in stimulus inputs.  Similarly, psychologists who are interested in consciousness will bear in mind that they're studying conscious recollective experience -- and not simply the processing of information stored in memory.

Moreover, it's important to remember that there are lots of different special or altered states of consciousness that are relatively poorly understood:

Although they don't usually get discussed much in psychology texts, all these phenomena can be studied using the tools of experimental psychology and cognitive science.

And because these are all essentially subjective states of mind, experimental research on their nature exemplifies the program of conducting an epistemically objective scientific analysis of ontologically subjective mental states. 

Finally, it's important to remember that studies of the development of the theory of mind are also studies of the development of consciousness -- provided, of course, that researchers actually think of their studies that way.

Of course, research on consciousness loses some of its interest-value if consciousness proves to be an illusion, or epiphenomenal, after all.

Which brings to mind an incident that occurred at Berkeley during the Fall Semester 2004, following a colloquium sponsored by the Institute of Cognitive and Brain Sciences.  After leaving campus for his home institution, the speaker wrote to his UCB host, informed him that he had lost his PalmPilot PDA during his visit, and asked if anyone might have seen it.

The speaker in question was Prof. Daniel Dennett of Tufts University, famous -- or is it notorious? -- for arguing that consciousness is an illusion -- that consciousness literally doesn't exist.

The date of the colloquium was September 17, 2004, and the title was "The Personal Level and the Decomposition of Qualia".  In his talk, Dennett argued that the "personal level" of analysis was equivalent to folk psychology, and that folk psychology was false just like folk physics is.  At least, you can't count on folk psychology to be true, and the only real psychology is equivalent to neurophysiology or cognitive neuroscience -- because it provides an objective, third-person description of objectively observable events.  He also asserted that qualia were intrinsic but nonfunctional features of experiences.

Which got me thinking:  How did Prof. Dennett lose his PalmPilot -- or, more precisely, How did Prof. Dennett realize he lost his PalmPilot?

Which got me thinking: Can a zombie lose his PalmPilot?  Not what Chalmers calls a philosophical zombie -- a creature that can do all the things a human does, but which lacks consciousness.  The philosophical zombie forecloses any discussion of what the behavioral consequences of conscious might be.  But rather what Chalmers calls a Hollywood zombie -- a true zombie, a creature that simply lacks consciousness (much as Haitian zombies lack a soul, or free will). 

It seems to me that true zombies can't lose their PalmPilots the way that Prof. Dennett did, because they can't realize anything at all.  In particular, zombies are unconscious stimulus-response machines (where the stimulus = human flesh and the response = eating).  Stimulus-response machines, whether Flourens' decorticate pigeon or a human being on automatic pilot, respond to the presence of stimuli in their environment; but they can't respond to the absence of such a stimulus.  They're not aware of what they're doing, and so they have no way of recognizing that they can't find what they want, or that what they believe isn't true.

So, maybe consciousness has a function after all.

Consciousness is part of the "package" given to humans by virtue of the evolution of mental life.

Presumably, intelligence came first, a product of the massive cerebral cortex characteristic of primate brains, which yielded massive general information-processing capacity. 

Then language emerged as a specialized mental module, associated with specific brain systems.

And also consciousness, defined as a capacity for awareness of internal mental states and behaviors.

Together, language and consciousness created the possibility for human culture -- defined by a set of institutions, like schools and universities, by which one person can deliberately teach another person what he or she knows.  Without the awareness of what one knows, and what another one doesn't, and without a means for efficiently transmitting that knowledge from one person to another, it's hard to see how complex culture could ever arise.  Put another way, the institutions of culture, especially those sponsoring what Bandura calls learning by precept, as opposed to imitative learning by example, presuppose consciousness.

Put another way: consciousness makes culture possible.

It's not entirely clear which came first, language or consciousness.  But it's pretty clear that consciousness is what gives us something interesting to talk about (cartoon by Tom Toro, New Yorker, 12/05/2016).

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So if consciousness is the great gift of evolution, and what makes culture possible, we probably should take it seriously.  As the Greeks put it on the Temple of Apollo at Delphi, we should strive to know ourselves.  Or, as the Thane of Cawdor put it on the entrance to his castle, "Be Mindful".