This method is primarily an “attack” method in that it is typically used when arguing against a view or position. It is generally not used when defending a position-except in terms of defending a position by criticizing another view.
Concepts & Method
This method is based on a basic concept in logic, that of logical consistency. Two claims are consistent when both can be true at the same time. For example, the claim “lying is sometimes acceptable” is consistent with the claim “lying is sometimes unacceptable.” This is because both of these claims could be correct. Two claims are inconsistent when both cannot be true at the same time (but both could be false). For example, the claim “national health care would do more good than harm for America” is inconsistent with the claim “national health care would do more harm than good for America.” This is because while these claims cannot both be true at the same time, they could both be false. National health care might, for example, be neutral in terms of overall benefits and harms.Because of the nature of inconsistent claims, if someone makes inconsistent claims, then at least one of their claims must be false. Similarly, if a person accepts principles that are inconsistent or entail inconsistent claims, then at least one of the principles must be flawed. This assumes, of course, that principles have truth values. Not surprisingly, theories must also be internally inconsistent-a theory that has inconsistencies must contain at least one false claim.The fact that two (or more) claims are inconsistent does not show which of them is false-the inconsistency just shows that they all cannot be true at the same time. Sorting out the true from the false is another matter entirely.Given that logically inconsistent claims cannot be true at the same time, it is irrational to accept such claims when their inconsistency is known. This fact provides this method with its ‘teeth.’
The method is as follows:
Step 1: Show that two claims made by a person or principles held by a person are inconsistent.
Step 2: Conclude that both cannot be true/correct.
For example, suppose that during the course of a conversation Ann seems to accept the principle that people should be treated equally but she also asserts that certain people should receive special treatment. On the face of it, there seems to be an inconsistency here: If people should be treated equally, then certain people should not receive special treatment. But, if some people should receive special treatment, then all people should not be treated equally. Therefore, one of the principles must be incorrect.Of course, the fact that there is an inconsistency does not show which claim or principle is mistaken-it just shows that at least one must be incorrect. Unless, of course, there is a reasonable way to respond to the charge of inconsistency.
Responding to a Charge of Inconsistency As with most attacks and criticisms, there are ways to respond to a charge of inconsistency. One way is to abandon one of the inconsistent claims or principles. Obviously, the least plausible claim or principle should be the one rejected. For example, Ann might decide to abandon the principle that some people should receive special treatment and stick with the principle that people should be treated equally. Naturally, this is not really much of a defense. However, if there are excellent reasons to reject one (or more) of the principles or claims, then this can be the logical thing to do.In some cases it is possible to respond to the charge of inconsistency by dissolving the inconsistency. This can be done by showing that the inconsistency is merely apparent. This is achieved by arguing that the claims/principles are actually consistent. For example, Ann might present the following reply: Treating people equally requires providing special treatment to certain groups or people. For example, allowing equal access to public facilities requires provided some people with special treatment in the form of ramps and special parking. Thus, the inconsistency has been dissolved.
Relativism, Subjectivism and Nihilism For two claims to be logical consistency they must be such that they can actually be true or false (but not both at the same time). If the claims are such that they are relative, subjective or without any truth value, then the situation becomes rather problematic. Ethical relativism is the view that the truth of a moral statement depends on the culture. Obviously, cultures with different moralities will present claims that are inconsistent with each other. Assuming this theory is correct, the truth of such ethical claims depends on the culture, so that a claim can be true in one culture and false in another. Hence this sort inconsistency is not a problem (assuming that ethical relativism is correct). Even on the assumption that ethical relativism is true it is still possible to apply a charge of inconsistency-but only within that culture. For example, in the 1800s American social morality (as expressed in the Declaration of Independence and countless speeches) held that all men are equal. Yet, slavery was also accepted by the culture, thus making it at least morally tolerable. Obviously the acceptance of slavery and the professed value of equality are inconsistent with each other. Hence, one of those views must be mistaken-within the context of American culture. Of course, a culture could accept as a moral principle that moral inconsistency is morally acceptable. In that case, the charge of inconsistency would bear no weight (assuming that relativism is correct). Ethical subjectivism is the view that the truth of a moral statement depends on the individual. Individuals with different moralities will obviously present claims that seem to be inconsistent with each other. For example, one person might claim that abortion is morally acceptable while another person endorses it. If ethical subjectivism is true, the truth of each moral claim depends on the individual, so a claim can be true for one person and false for another. In this case, inconsistency is not a problem because it simply cannot occur between individuals. Everyone is correct because morality is subjective. However, even if subjectivism is true, a person can be charged with inconsistency in their principles and claims. However, a person could hold that moral inconsistency is perfectly acceptable and if subjectivism is true they would be right. Moral Nihilism is the view that moral claims have no truth value-they are neither true nor false. If moral claims are neither true nor false, then there is no possibility of logical inconsistency between moral claims .Hence, if moral nihilism is correct, then inconsistency in regard to moral claims and principles is impossible.