Ned Block's article "Troubles with Functionalism" is a fascinating read that challenges its readers to, in the least, question functionalism; and potentially even consider it an unbelievable physicalistic thought process. The nature of the article is such that each particular section builds upon the one before it, which adds a sense of depth to his primary argument against functionalism because he enlightens his potentially unenlightened reader (myself in this case) about the nature of functionalism as well as other specific concepts prior to even giving his opinion. This build-up gives Block more credibility because it makes his argument much more sincere in nature. In order to successfully state and analyze Block's objection to functionalism, a brief overview of functionalism is in order.
While there exists multiple forms of functionalism, the primary concept is that mental states are seemingly dependent on their functional role. In essence, functionalism views mental states in a sort of cause-and-effect scenario. Mental states do not exist in any way separate from the physical body (outright rejection of Cartesian dualism), however there is not a strict sense of a materialistic point of view (or a behaviorist for that matter) either because there is still a capacity for some state, one that is called the "mental state", however its true quality is ultimately dependent on the body; however in some other respects exclusive from it. Undoubtedly, functionalism seemingly takes the philosophical middle ground; which lends some reasoning behind why it has grown in popularity in contemporary philosophy. While I find the argument of functionalism to be very intriguing, I also find it to only be a particular account for the mind/body that can be fully believed if one suspends belief in reality. On the surface functionalism is a very attractive belief, however I would assume many arguments have been made against it because it lacks definitive accounts for issues that have been considered in other philosophy of the mind theories. In the case of Ned Block's article, "Troubles with Functionalism", he primarily focuses on the lack of acknowledgement of the qualia (subjective conscious experiences).
Ned Block's argument is somewhat complex to grasp, however I will do my best to successfully describe it as I perceive it (note: this subjective perspective as it relates to my interpretation relative to another individuals will in some ways bring his argument to life). To philosophically standardize Block's argument against functionalism (specifically, machine functionalism), he asks if there "..is anything which it is like to be the homunculi-headed system"? (217). He calls this argument the "Absent Qualia Argument". This singular statement ultimately defines Block's argument, and it is reasonable and logical that he raises this particular critique against the functionalist point of view.
Block's hypothetical (yet logically possible) argument begins by laying the groundwork for a functionalist's Turing machine. While this system is theoretical (as it is meant to be), it brings to light the reality of the functionalist's viewpoint. Block first envisions a "homunculi-headed robot" (which later is slightly altered into the "Chinese system" for the sake of realism) consisting of a billion individuals essentially acting as part of a computer process. These billion little beings all function in specific ways (like neurotransmitters) and at specific times relative to specific inputs, however the reactions are always the same so long as the same variable factors are occurring in an orderly process. In the functionalist's view, the robot, China, and every individual (specifically the reader as Block points out) function through a specific set of inputs and outputs. Block's argument is made whole when he gives a hypothetical analogy that in many ways "disrupts" the "computer" processes present by considering what would occur if freak accidents (such as a flood or a disruption in the radio signal). According to the functionalists' stance, nothing particularly unusual (or, at least, unexpected) would occur because the nature of the functionality of the system is written into the underlying algorithm of the "computer", "China", "the universe", or what have you. One who does not accept the functionalist point of view, like Block, however is prone to ask if this is really possible (and if it is envisionable, is it logical and capable of existing even in some small scale way). If one examines basic elements of the chaos theory, one would undoubtedly be forced to remove any capacity for unexpected, subjective, and chaotic elements to come into the functioning of the machine. There is a direct correlation between functionalism and structure, which inevitably is the primary point of this theory of mind. Finally, according to Block, the examples proposed about the "homunculi-headed robots" and "China" are prima facie counterexamples to machine functionalism because we have the capacity to rationally and logically doubt that mentality exists within such a structured system. Furthermore, mental states can not be identified with functional states if a functional state can create a mental state in some situations (realistically speaking, think of human beings being capable of conscious cognition) yet not in others (some lesser-animal who have brains but are unable to have a mental state, or even more noticeably in an inanimate object).
For myself, Block's argument is very sensible and on the whole I agree with him (or minimally, his reasoning as to why functionalism that be a fallacy). There is undoubtedly something to be said about qualia when one considers the functionalist's viewpoint, seeing as there are little grounds for true subjective experience to occur. However, to play devil's advocate and oppose Block; one could question why qualia is important at all. Is it not imaginable that we exist in a structured universe with no true chaos (though, we may perceive it as chaos because of how the algorithm we live in allows us to have this perception)? Qualia alone does not seem to be the deciding factor as to whether or not the functionalist theory is correct or not. With that said, I feel Block has ultimately begun to chip away at the logic behind functionalism; though we may never be certain as to whether or not the world we live in functions in a chaotic way or is structured. The question of chaos/structure is ultimately what would determine the accuracy to any theory of mind.
As far as the functionalist's view is concerned, I do not agree with it, nor do I whole-heartedly disagree with it as of this moment. It is, perhaps, a theory that needs to be better developed to make more sense to me; however as it is right now, I feel it is catering solely to those who desire to be content without actually having to choose an extreme of materialism or dualism. As a materialist myself, I find this argument to be for the weak-minded who are not willing to acknowledge unknown variables that exist in our universe.