Much of the debate regarding dualism can be attributed to the use of the term itself. Around 1700, Thomas Hyde coined the term 'dualism' to refer to theological theories that advocated two ultimate principles ("Monism and Pluralism" 364). Presently, the term has developed a systematic ambiguity, a consistent variation of meaning according to context. Metaphysical dualism can be defined as any view in which two ultimate, irreducible elements or aspects constitute a given domain (Blackburn 110). These elements are not only distinct, but also irreparably separate – different in kind, not degree. Technically, metaphysical dualism posits two genuine orders of existents with completely independent ontologies (Griffin 129). In contrast, epistemic dualism posits two primary categories of existents with similar ontologies. These elements are abstractly distinct yet concretely inseparable.

This paper considers which contexts are logically untenable for a dualistic system. Three main contexts contribute to the systematic ambiguity of the term 'dualism.' These contexts are epitomized in three questions: (1) What is reality composed of at the most abstract level? (2) How is reality manifested? and (3) How is reality understood (by us)? Questions (1) and (2) are metaphysical; question (3) is epistemic.

Any answer to question (1), be it dualistic, monistic or pluralistic, can neither be accepted nor rejected by immediate empirical evidence. For if the proposed answer describes reality, then the answer will encompass the entire reality. But the entire reality can never be empirically viewed as it is; one cannot step beyond the bounds of reality to observe it. No matter how large a part of the reality is experienced, no matter how comprehensive a theory becomes, the function and composition of the entire system is forever beyond the grasp of experience. As for a rationally based answer to question (1), the theory will possess influence only so far as it accounts for answers to question (2).

Answers to question (1) can be mediately criticized on the basis of answers to question (2). The ultimate metaphysical components of reality can be manifested rationally or non-rationally. If these elements are manifested non-rationally, then there is no logical link between the metaphysical elements and the manifested reality. As such, one can neither argue for nor against theories of the metaphysical composition of reality. Since the metaphysical composition of reality can neither be known empirically or rationally, all such metaphysical theories become nothing more than mystical insights divorced from metaphysical criticism.

In contrast, if the ultimate metaphysical components of reality are manifested rationally, then there is a logical link between the composition and manifestation of reality. Metaphysicians and physicists usually hold this position, trusting that "the ultimate natures of things lie together in a harmony which excludes mere arbitrariness," a "harmony of logical rationality" that "lies upon the universe as an iron necessity" (Whitehead 18). Indeed, reality appears to function as a logical order, bestowing "a rational unity on the cosmos" (Davies 170). Even chaos theories and quantum indeterminism espouse that an essential order pervades chaotic systems (Butz par. 2).

Given that a subtle order permeates all functions of reality, certainly the manifestation of the metaphysical components of reality will occur in a logical order. However, if the manifestation of such metaphysical elements cannot occur in a logical manner, that metaphysical system will never exist in reality and, as such, that system can be dismissed as errant and irrelevant to reality. In fact, this paper argues that any answer to question (2) is either logically impossible or overcomplicated; therefore, any metaphysical dualism proposed in response to question (1) is invalid. In addition, this paper contends that any metaphysical dualism is a misinterpreted epistemic dualism.

(1) What is reality composed of at the most abstract level? Metaphysical dualism proposes two essential answers to this question: attributive and substantial metaphysical dualism. Attributive metaphysical dualism acknowledges the plurality obvious to our experience, yet classifies the many types of existents as elements within two essential kinds of existents. Substantial metaphysical dualism is the more extreme system, limiting reality to two kinds of substances manifested in various modalities.

While these answers can neither be accepted nor rejected by immediate logical argument, it may be interesting to note some possible effects of such a metaphysical position. Psychologically, dualism promotes self-preservation (Shobris par. 1). Questions concerning suffering and injustice readily transfer to an alternate reality free from the evils of this world. Most world religions teach that human consciousness, while divided, can be reunited with the source of being through spiritual death and rebirth (Kramer 187). By allowing a distinction between the world and an afterlife beyond the world, dualism circumvents the emotional fear and dread of aging and eventual death (Shobris par. 21). Thus, dualism assists us in coping with the inevitability of death and the pervasiveness of suffering.

Physiologically, dualism may be caused from an over-emphasis on left-hemispherical thinking (Shobris par. 25). Neurological studies have shown that, in general, the left hemisphere of the brain primarily performs analytic operations; the right hemisphere, primarily synthetic operations. Thus, an excess of analysis without a complementary synthesis may very well produce an unreconciled dualism. This criticism concurs with the observation that dualism is often the product of failed monism ("Monism and Pluralism" 364). Socially, due to an isolation of possible experiences, metaphysical dualism encourages shallow emotional consolation without strengthening or illuminating the qualitative experiences of human life (Dewey 524). By creating obscurity, confusion and inconsistency, dualism potentially enforces unjust social structures by producing a division between present conditions and a more desirable condition, leading to a struggle from the present to the more desirable (Shobris par. 27).

Scattered among his writings, Charles Hartshorne denounces many philosophical features of metaphysical dualism. Hartshorne labels dualism as "simply the refusal or failure to achieve a general theory . . . in which only details are set aside and even unmanageable generalities are given their due in whatever way possible (ZF 97-98). His view concurs with other scholars, who dismiss the "confusion" of dualism as "a failure to understand the nature of the problem, or rather to recognize that it is not a real problem at all, but a pseudoproblem" (Hintz 104), or criticize dualism for accepting the superficial as the actual due to inadequate investigation (Shobris par. 58). Hartshorne further criticizes dualism as a postponement, rather than a solution, to difficult problems (IO 133), as a mere label to a problem and a solution to nothing (ZF 133). Reflecting the attitude of much modern science and philosophy, these scholars express an inherent distaste for metaphysical dualism.

(2) How is reality manifested? There are three possible manifestations of a metaphysical dualism: reality as (a) a product of the tension or contrast between two kinds of elements, (b) a product of a complete synthesis between two kinds of elements, and (c) a product of reciprocity or degrees of combination of two kinds of elements. In the following arguments, the dual aspects of experience will be represented by the symbols A and Z, where A represents the domain of one kind of element, Z the domain of the other.

(a) A metaphysical dualism of contrast explains the reality AZ(C) as product of the tension/contrast between two genuine kinds of existents, A and Z. Furthermore, in such a dualism, neither A nor Z are present in the product. Any product created by the tension between A and Z lies somewhere between A and Z. For example, two magnets of opposite charge can produce a magnetic field, yet the magnets themselves are not present in the magnetic field. Since neither A nor Z are present in the resultant product, there is no way to validly infer the existence of A or Z. For if either A or Z are present in the product, there is no longer a dualism of contrast. Without any presence whatsoever of A or Z, only the wildest speculation could correctly guess the origin of the product AZ(C). As the magnetic field in no way resembles the magnets responsible for its existence, it is more likely that the product of a duality of contrast in no way resembles the elements responsible for its constitution. The postulation of A and Z in a duality of contrast is not only impossible, but also meaningless, as we would have no idea at all of the qualities of A or Z because they are, by definition, not at all present in AZ(C). (b) A metaphysical dualism of synthesis explains the reality AZ(S) as a product of complete synthesis between two genuine kinds of existents, A and Z. By definition, A and Z are entirely A and Z, respectively (i.e., A does not also include another element B). Therefore, A and Z can be abstractly "divided" into AA and ZZ. A Punnett square illustrates the result of a cross between AA and ZZ:

There is a 100% probability that a synthesis between AA and ZZ will produce AZ(S). As neither kind of element in a dualism predominates over the other (or else the dualism would become a weighted monism), the product AZ(S) is neither A nor Z, but quite distinct from both A and Z. In fact, both A and Z are no longer present in the product AZ(S); in a sense, they have vanished.

If neither A nor Z are present, how can they be known? If A and Z were hypothesized to be the primary kinds of elements constituting AZ(S), there would be no way of verifying that hypothesis. A product AZ(S) can not only be produced by a cross between A and Z, but also by a cross among AZ(S) itself. For example, in certain species of chickens a cross between black-feathered (AA) and white-feathered (ZZ) chickens produces Andalusian blue-feathered (AZ(S)) chickens (Hickman 158). The cross does not produce gray-feathered chickens, the combination that would hint at an origin of black and white-feathered chickens.

In fact, if you begin with the blue-feathered product and work backwards, you will find that blue-feathered chickens are not only caused by a cross between black and white-feathered chickens (AA x ZZ), but also by a monistic cross between blue-feathered chickens (AZ(S) x AZ(S)) (Hickman 159). In more general terms, a product AZ(S) is not only caused by a dualistic synthesis of AA and ZZ, but also by a monistic synthesis of AZ and AZ. This latter result can also be illustrated in a Punnett square:

Thus, the separation of AZ(S) into AA and ZZ is just as probable as the assumption that AZ(S) did not arise from AA x ZZ (dualism), but from AZ x AZ (monism). In fact, the latter assumption not only accounts for AZ(S), but also provides, by the presence of AA(S) and ZZ(S), misleading evidence for the former dualistic assumption.

(c) A metaphysical dualism of reciprocity explains the reality AZ(R) as the product of degrees of combination between two genuine kinds of existents, A and Z. The ancient religions of Manicheanism and Gnosticism held cosmic dualisms of reciprocity (Burkitt 17; Yamauchi 15). Each element of reality AZ(R) is seen as the result of varying combinations of A and Z. As gray is a mixture of white and black, experience is a mixture of members of A and members of Z.

However, given that A and Z are opposed domains, Z is equivalent to the opposite of A. Evil is as much the opposite of Good as the negation of Good. The relationship between A and Z can also be construed as the relationship between A and ~A, illustrated below:

º

Darkness is as much the opposite of light as it is the absence of light. Furthermore, that A may only have meaning in relation to Z does not imply that Z must exist in order for A to exist (Singer "The Polarity Fallacy" 73). Therefore, the original dualism of A and Z is more simply a monism of A, where the product AZ(R) is the relative presence of A rather than the degrees of presence and absence of A and Z. Following Plato and Augustine, darkness is not an element in itself, but rather the absence of light. The reduction of a dualism of reciprocity to a monism of relative presence produces an equivalent explanation, an equivalent result and, more importantly, a simpler theory.

Apart from these specific objections, the manifestation of metaphysical dualism involves two general faults. If reality is the product of A and Z, then such a theory is, in fact, not dualistic. A third element becomes essential to complete the explanation of reality, namely the product itself, which is neither A nor Z, and possesses an entirely distinct ontology, AZ, that mysteriously combines the properties of A and Z. Thus, either the elements of a dualism are irreparably separate in reality as well as in theory, or the dualism metamorphoses into a pluralism by the presence of an entity embodying an interaction between A and Z. Experience generally opposes the first alternative, while the second hypothesis can be explained equally well solely on the terms of entities of the kind AZ. Given this latter alternative, A and Z are merely dual epistemic subdomains within the true metaphysical domain AZ.

In order to avoid the first general fault, metaphysical dualists often select a particular entity in one ontological domain as the locus of interaction between the dual domains, thereby eliminating the need for a third kind of entity. This is the second general fault of metaphysical dualism. First of all, why is the particular Z(1) within domain Z the locus of interaction between A and Z? What distinguishes Z(1) from Z(n)? To be consistent, why not allow all entities in domain Z as loci of interaction, abandoning the complicated dualism for a much simpler theory in which the reality AZ manifests itself as two (epistemic) types rather than two (metaphysical) kinds? Furthermore, this solution subtly ignores the nature of a dualism. The particular entity Z(1) responsible for the interaction between the dual domains A and Z does not possess an ontology completely independent from its opposite domain, for the particular entity Z(1) must somehow be related to domain A in addition to domain Z in order to provide the possibility of interaction between A and Z.

Given these arguments concerning the manifestation of metaphysical dualism, it should be clear that any dualist answer to question (2) can be shown to be either logically impossible (a, general faults) or equally explained by a simpler theory (b, c, second fault). Therefore, any answer to question (1) can be regarded as superfluous, for a dual-composition reality cannot be efficiently and logically manifested. Thus, metaphysical dualism is not only inherently distasteful, but also logically fallacious.

(3) How is reality understood (by us)? The specific and general objections to the manifestation of metaphysical dualism lend themselves in support of epistemic dualism. After all, some sort of dualism presents itself in nature, thereby giving rise to dualistic theories. The debate regarding mind-body duality is a classic example. But, as has been shown, the dualism present in nature is not metaphysical. More likely, theories of dualism are a result of the way we experience reality. As such, we can validate and incorporate the dualisms present in our experiences by developing a system of epistemic dualism. In the words of Hartshorne, the "admission of ultimate dualities is one thing, [metaphysical] dualism is quite another" (ZF 109). In fact, insistence on a dualistic system becomes more tenable by combining two metaphysical kinds into one metaphysical kind with two epistemic poles that complement each other,⁽³⁾ thereby avoiding the quandaries of manifestation and interaction.

Having analyzed philosophical dualism, two important conclusions emerge. (1) The division of any given domain into an ultimate metaphysical dualism is either unnecessarily complicated or logically impossible, validating an intuitive distaste for dualism held by many philosophers. However, the error of metaphysical dualism does not provide sufficient ground for the wholesale dismissal of dualism as a theory. Rather, the analysis tends to expose metaphysical dualism as the "refusal or failure to achieve a [more] general theory." (2) Epistemic dualism provides a theory able to acknowledge the seeming evidence for metaphysical dualism while avoiding metaphysical obstacles. In fact, evidence for epistemic dualism emerges through the criticism of metaphysical dualism. The challenge of dualism is to find (metaphysical) coherence in what appears (epistemically) irreconcilable.

1. All thinkers of whom we know enough to say anything definite on their position, up to and including Descartes, were dualist interactionists" (Popper 152). See also Hussey 32-33.
2. A Defense of Dualism," Foster considers four questions central to the debate of mind-body dualism, here briefly posed:
   
   1. How can a nonphysical mind causally affect a physical body?
   2. What is the relation between mental events and neural events?
   3. How can there be psychophysical laws?
   4. What is the causal influence of mind on body and body on mind?
   All of these questions address the specific relationship between mind and body.
3. See Hartshorne's "A Logic of Ultimate Contrasts" in The Zero Fallacy and Other Essays in Neoclassical Philosophy for an example of an epistemic dualism. Also see Singer's "Polar Terms and Interdependent Concepts" for a discussion of three different conceptions of polar terms and their relations.

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