Is consciousness a byproduct or “add-on” of our evolution or is it something that is intrinsic and inseparable from the skills we humans have? I know this question sounds strange but it's something that has bugged me for quite some time.

I don't think your question is strange at all. In fact, many philosophers of mind have been pre-occupied with just this very question for quite some time. Then again, perhaps that just makes us strange!

It might help to start by being clear about what exactly you mean by consciousness. Sometimes we talk of being conscious in the sense of being awake as opposed to being asleep, or as opposed to being passed out after an overindulgence of some sort. Sometimes we talk about being conscious in the sense of being aware, so we might sometimes be conscious of the ticking of the clock and sometimes not. Philosophers often talk about consciousness in a third sense to refer to the subjective aspects of our experience. To use a phrase brought into play by Thomas Nagel, there is "something it is like" to smell coffee brewing, or to see the vivid colors of a sunset, or to have a sharp pain in your toe. This is often referred to as phenomenal consciousness, and trying to find some way to account for it has become known (following David Chalmers' work in The Conscious Mind) as "the hard problem of consciousness." What makes the problem so hard is that it seems that phenomenal consciousness is not just built in to the brain, and so it's hard to know how we can account for it. It seems that we could imagine all of our neural mechanisms being exactly the same as they are and yet we might lack consciousness. Chalmers makes this point through the example of our zombie twins. Philosophical zombies aren't like the zombies of horror movies. They don't eat flesh, for example. They are supposed to be exactly like we are--molecule for molecule identical to human beings--but without any phenomenal consciousness. All is dark inside. So both zombie Amy and I might be typing at our keyboards, but whereas I am having the experience of feeling the keys touch my fingertips, and whereas I am savoring the delightful taste of the Diet Coke I just had a sip of, zombie Amy doesn't have these experiences while she types and sips. She types and sips without feeling or tasting anything at all. If zombies are conceivable, and many philosophers have thought they are, then it does indeed seem like consciousness is an "add-on" to the physical stuff we're made of. It doesn't seem intrinsic to the skill of typing, say, that one would have to have the phenomenal experience of feeling the keys on our fingerstips.

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