This sort of outlook fits well into Fodor's driving point regarding psychology: human behaviors can be understood as valid arguments relating intentional states of mind. In physics, when observable phenomena disagree with our understanding of the rules governing the physical world, it is not assumed that some other mystical force is at work -- merely that our observations or concepts concerning physics must somehow be mistaken in that specific situation. Furthermore, it is not assumed that we cannot know what caused the disparity between prediction and observation -- merely that it requires further inquiry. Similarly, Fodor does not assert that the workings of the mind cannot be understood because we may be unable to directly observe them, nor does he contend that something nonphysical is at work when disagreements occur. Fodor's physicalism approaches the mind from the perspective that the mind is a complex physical system, and that mental states must, accordingly, be physical properties of an individual's mind. The most obvious difficulty with this sort of approach to the mind is that the relationship between the physical world and an equally physical interpretation of it in the mind is not altogether apparent. If reality is the complete sum of physical objects, it is hard to imagine how a physical mind could be capable of possessing an infinite number of physical bits of information and also rely upon rational thought processes (Cain, 16). Much of Fodor's philosophy can be seen as a response to this age-old dilemma. He seeks to deliberately place folk psychology within his overall physicalist framework in order to justify the former and provide a guide to how a better functioning form of cognitive science might be approached. Since he embraces both physicalism and folk psychology, Fodor is faced with the task of explaining why our subliminal understandings of psychology should be accurate within the physical world. Problems arise with this model of the mind when modularity is reconciled with causal reference. Fodor brings these two notions together as a result of his competing psychological and philosophical pulls, but the consequences are somewhat dubious.

Despite his firm belief in commonsense psychology, Fodor takes a drastic step out of it when he issues his support for modularity within Modularity of the Mind. He writes, "Behavior is organized, but the organization of behavior is merely derivative; the structure of behavior stands to mental structure as an effect stands to its cause." (Fodor 1983, 2). With this statement he illustrates his affiliation with folk psychology in that he draws a connection between observable behavior and perceived mental causes of that behavior. However, his reverence for physicalism means that his next question demands a sufficient answer: "But whereof does the structure of the mind consist?" (Fodor 1983, 2). Because of this question, Fodor is forced to engage in a discussion regarding the possible architectures that could make up the human mind. He regards the mind as not a single entity that tallies and organizes information throughout its structure, but as one composed of different systems that are related but discrete. Superficially -- from the folk psychology perspective -- the mind may seem to act as a single system, but Fodor cannot embrace this notion because the mind must be bounded.

In general, "There are two dimensions along which distinct modularity theses may differ. First, they may differ with respect to the account of the nature of mental modules that they incorporate.... Second, they may differ with respect to their account of the number and identity of the mental modules in the human mind." (Cain, 184). In other words, advocates of modularity in the human mind routinely disagree over specifically what a module is, and how many of them occur in the mind. Accordingly, it is essential to place Fodor somewhere within this spectrum: he believes that modules are entirely specific to the tasks they perform, and that the human mind holds at least six of them. But in order to keep his conception of folk psychology sound, he also recognizes that many of the observable human behaviors come from a functioning of the mind that is not modular: "High-level perception and cognitive systems are non-modular on Fodor's theory." (Prinz 2005). Nevertheless, Fodor justifies modularity in such a way that it can be applied to more extreme versions of the theory.

Modularity -- to most philosophers of the mind -- is a more strict and controversial extension of functional decomposition. This is the idea that the mind contains systems...

The essential claims of modularity refer to what these systems might be like, how they might operate, and how they might relate to one another. Fodor's individual brand of modularity is characterized by nine properties: (1) they are localized with respect to the brain; (2) they are subject to characteristic breakdowns; (3) they operate in an automatic manner; (4) they perform their duties quickly; (5) they have simple output functions; (6) they develop in a particular order and speed; (7) they operate within a set framework of inputs; (8) they are inaccessible to the higher level systems of the mind; and (9) they cannot be influenced by the higher levels of the mind (Fodor 1983, 47-100). He explains, "The modularity of the input systems consists of their possession of most or all of the properties now... enumerated. If there are other psychological systems which possess most or all of these properties then, of course, they are modular too." (Fodor 1983, 47). This is a rather strange assertion because Fodor does not make it clear exactly what his list of nine criteria is intended to accomplish. The words "most or all" suggest that if a mental system satisfies five of the criteria then it is a module; however, it is not obvious why this should be true. One critic has wondered, "Perhaps a system is modular to the extent that it exhibits properties on the list. Alternatively, some of the properties may be essential, while others are merely diagnostic." (Prinz 2005). In short, the list itself is questionable in its organization and function; so too are several of its portions.
Fodor's first and most powerful premise is that the brain exhibits localized functions. He points to a handful of experiments which indicate that this may be the case with reference to certain forms of input and response. Color perception, analysis of shapes and regions all display evidence of being regionally organized within the brain; yet, despite indications of some consistency concerning these possible modules, many independent studies have concluded that sight perceptions have been identified as being located in many regions across the brain (Cain 87). Nevertheless, Fodor uses this premise to assert, "Since the satisfaction of the universals is supposed to be a property that distinguishes sentences from other stimulus domains, the more elaborate and complex the theory of universals comes to be the more eccentric the stimulus domain for sentence recognition." (Fodor 1983, 51). From this, he concludes that this eccentricity can only be accounted for by inputs from multiple modular systems. Accordingly, he rejects the idea that a mechanism used for facial recognition, for example, could ever be involved in the sentence recognition which must occur elsewhere.

The major trouble with this premise is that the level of localization of brain functions that has been observed in the lab does not adequately support the strong levels of localization that would back modularity. "Evidence for strong localization is difficult to come by. Similar brain areas are active during multiple tasks, and focal brain lesions tend to produce multiple deficits." (Prinz 2005). The unanswered question, to Fodor, is how the unspecific nature of the input domain results in the specialization of the metal mechanisms at work. He leaves this objection relatively open, but is optimistic that localization holds-up irrespective of the manner by which information is received.

Fodor also agues that modules are mandatory, fast, and shallow. Essentially, some mental processes are not mandatory, in that we can choose whether or not to do them; but to Fodor, modules exhibit the characteristic that we cannot choose whether or not to do them. "For example, if you hear a sentence of a language that you know then you cannot help but hear it as a sentence; you do not have the power to 'switch off' the processes that result in your hearing it as a sentence as opposed to a pure sound." (Cain, 186). Yet, although we may automatically recognize colors, objects, or words, we retain the capacity to manipulate them as we see fit. We can devise any sentence we want, imagine any assortment of colors we want, or organize objects in our mind however we want. Certainly this ability must be related to our knack for recognizing these things quickly and without deliberation, but this is not addressed by Fodor.

Furthermore, quickness -- in itself -- truly implies nothing concerning modularity. In truth, virtually every function a module could carry out will be carried out at…