I am standing in front of you, and so I am aware of you, that is, I am conscious of you. The reductionist next to me assures me that my awareness of you is nothing more than neurochemical activity. Thus, he has reduced consciousness in general to neurochemical activity. Keep in mind, however, that as I am aware of you, I am not aware of any neurochemical processes taking place in my brain; I am simply aware of you and the surrounding area. Thus, for me, my awareness is not identical to any neurochemical activity taking place within me; for the reductionist, the two are one and the same.
Let's imagine a situation in which I am sitting in front of you, aware of you and everything you are doing (sipping a cup of coffee, crossing your legs, looking out the window, etc.), but the reductionist researcher is monitoring only the neurochemical processes taking place in me - in other words, from his angle, he cannot see what I am seeing. Since he has identified my perception and awareness of you with neurochemical processes in my brain, and since he is aware of those neurochemical processes of which I am not aware, then it would seem to follow that if he is right, he should be aware of my awareness of you.
Of course, he is not aware of you; I am aware of you. He is aware of something that is happening in me, on a neurochemical level. Hence, he is not aware of my awareness of you; he has no access to that awareness; and yet he has identified my awareness of you with the neurochemical processes of which he is aware.
Let's pursue this a bit further. His awareness of the neurochemical processes that are occurring in my brain is, if reductionism is true, really nothing other than neurochemical activity in his brain. Thus, if my awareness of you is reduced to neurochemical processes of which he is aware, and his awareness of the latter is reducible to neurochemical processes in his brain, then it would seem that my awareness of you is nothing more than the neurochemical processes that are occurring in his brain. The problem, though, is that he is not aware of the neurochemical activity in his own brain, only in my own. So my awareness of you is reduced to something that neither I nor he (the researcher) is aware of.
Neurochemical activity, which is the object of his awareness, is just that, neurochemical activity, limited to itself. The reason I say this is because in knowing the neurochemical processes occurring in me does not allow him to become aware of what I am aware of - he has no access to my subjectivity. Moreover, that neurochemical activity that is going on in me is, as awareness, something that extends beyond me, that is, it is expansive. In other words, it embraces, it includes, it apprehends something beyond the self (i.e., you, what you are doing, and the environment that surrounds you). To apprehend in the ordinary sense of the word (such as apprehending a criminal) is to grab or hold; thus it is to be united to something. What this suggests is that awareness of something beyond the self - i.e., both sense and/or intellectual apprehension - is a possession of some kind. I am in possession of you and the surrounding environment. But I do not possess you physically or materially - you and the surrounding environment of which I am aware is not in me physically. It is, nevertheless in me, that is, I apprehend it (to some degree at least). In other words, knowledge is in me; I am aware of you and the environment. Thus, my awareness cannot be reducible to neurochemistry.
At best, we can say that neurochemical processes, that is, brain activity, is a necessary condition for sense and/or intellectual awareness. A necessary condition for something is not the same is that for which it is a condition. It is a condition for awareness of something outside the self, but it is not itself awareness of something outside the self.
Consider too that in order to know what this neurochemical activity is both in the here and now of his observation and in general, the reductionist has to know something first, something that the awareness of the neurochemical processes in particular and/or neurochemistry in general does not make known to him. He has to know from the inside that he is aware of an object, and only then does he proceed to study what is happening in the brain as he is conscious of something (such as what is happening in his immediate environment, i.e., his cat is walking around looking for food). He then knows that what is happening on the neurochemical level is related to his perception, that is, his awareness of the cat. It is not the neurochemistry that gives him this knowledge, but rather his initial perception and accompanying awareness that he is perceiving something that provides this knowledge. It is this perception and self-knowledge (subjective knowing) that allows him to know that what is happening in the brain is related to consciousness. The reverse is not the case - he does not come to know neurochemistry first and then becomes aware of his surroundings as a result of that scientific knowledge. Thus, sense perception and its accompanying awareness cannot be reduced to neurochemistry without destroying the science of neurochemistry (without awareness of something outside the self and its accompanying self-awareness, there is no science). In other words, the science of neurochemistry is possible only because there is consciousness. Neurochemistry does not explain it when neurochemistry requires it in order to achieve its status as a science, just as a science does not prove its own principles, but uses those principles to prove other things. It is consciousness that explains the possibility of neurochemistry.
What is happening to my sense organs in the course of sense perception, both external and internal sensation, will give evidence of itself in a way that is both empirical and measurable, at least to some degree. The reason is that sense organs are material. However, the activity of sense perception is the awareness of something outside the self, an awareness that does not change the object of awareness. So much more than neurochemistry is going on here.
Perhaps a metaphor will help to explain this. Imagine that I were to dump a pile of cooked spaghetti noodles onto a table. That's nothing more than a pile of spaghetti noodles on the table. But arranging the noodles into a configuration that spells out: "There is something in the fridge" is to add to the pile of spaghetti noodles. What do we add? We do not add anything material. There is no more matter on the table than there was before. There is, however, something more. Something immaterial has been added, namely information (form). You see the spaghetti noodles and your mind has been informed (given form or information). What is that information? It is a series of signs that together constitute a sentence. It indicates, it points in an immaterial way, that is, it signifies, or intends. What does it point to? It points to (immaterially, not materially like an arrow) contents in the fridge, that is, it points beyond itself. It turns my attention away from it towards the fridge. That is what information does, it signifies. What is happening to my brain and sense organs is that they are being specified in some way, and the neurochemical evidence for that can be studied.
But this specification is formal, not material (matter is not added in the act of sense perception), and the result is that information is being expressed. First there is impression - something is happening to my sense organs, and then there is expression or signification. This is what is meant by the "impressed sensible species" and the "expressed sensible species".
Information is expressed through the sensible species. But this signifying is different from the spaghetti. I notice the spaghetti, and then I notice the information it conveys, just as I notice smoke and then my attention is turned to the fire that is causing it (the former is a conventional sign, the latter is a natural sign). But I do not notice the impressed sensible species; I just receive the information. My attention is immediately turned towards the object of my awareness. Nothing is added to my senses materially, but something is added formally - just as nothing was added to the spaghetti materially, but something was added, namely form or information. My senses are formed in some way, specified, a sensible species is impressed upon them, and the result is information. The sensible species is a formal sign. It is information (like the spaghetti sentence), but it is pure information (unlike the spaghetti). A formal sign's sole function is to signify.
Now my activity of sensing is an instance of change (it is the realization of a potentiality), but I am not changing. I remain the same. The "I" that remains the same is acting or sensing. Thus, there is a real distinction between the self and the activity. And since temporal activity is the realization of a potentiality (if I am seeing, then it follows that I have the potentiality to see), then I must have a faculty or power to see. The single being that is me possesses a power, a potentiality to further activity, distinct from other powers (I.e., hearing, touching, smelling, etc.). The realization of that power requires a sense organ. Thus, I don't have the power to see and hear, etc., because I have eyes and ears, etc., rather, I have eyes and ears, etc., because I have the power to see, and hear, etc.; it belongs to my nature to see, to hear, to touch, etc., which is why the organism which is myself built its own eyes, and ears, etc.
Sensation is the realization of an existing potentiality, and the entire network of potentialities defines me (i.e., I am a sentient and rational substance). Something more than neurochemistry is occurring, at least more than what the idea of "neurochemistry" by itself contains; there is the actualization of a potentiality, and the sense organ is the necessary condition for that activity. Thus, neurochemistry as such is nothing more than neurochemistry, but sense perception is more than neurochemistry. If it were not, knowing neurochemistry would amount to becoming aware of the object of my awareness, and clearly the neurosurgeon who is observing my brain and perhaps stimulating parts of my brain is not experiencing what I am experiencing.
In sum, if reductionism is true, then becoming aware of the fact that all awareness is nothing but neurochemical activity is itself neurochemical activity. Hence, science is nothing but neurochemical activity. But science is a knowledge of neurochemical activity, not neurochemical activity (otherwise everyone who perceives would be a neurochemist); but the reductionist insists that all knowledge (including knowledge of neurochemical activity) is reducible to neurochemical activity (the one cannot be more than the other, thus awareness is not more than neurochemical activity). And yet, knowing your neurochemical activity does not give me a knowledge of what it is like to be you, that is, what it is that you are aware of, and vice versa.
There are two interiors in you, one to which we on the outside have access, and another to which we have no access. The former is your physical interior, the latter is your conscious interior. The former can become an object of scientific scrutiny (anatomy), the latter is subjective and private, and only you can unveil what is contained therein. The two are related, because you are a material thing, but the two are not identical, thus the one (consciousness) cannot be reduced to the other (neurochemical activity) without destroying it (consciousness). In other words, it is not subjective awareness that is reducible to neurochemistry, rather, neurochemistry is less than and is explained by subjective awareness.