The Taxi-Cab Fallacy is a complaint lodged by Christians apologists against one style moral objections to biblical authority. It is not a logical fallacy, and has no formal expression. In cases where the skeptic is inquiring into the moral reasoning of the apologist, it is not appropriate to refer to any move made by the skeptic as "fallacious." Fallacies can only occur within the context of an argument, and unless the skeptic is asserting propositions, it is impossible for the skeptic to make an argument that is fallacious.
It is asserted in the form of a metaphor from which the argument gets its name:
- Street Apologetics: "The “Taxi-Cab Fallacy” is committed when one hops in and assumes a certain system of thought or worldview in an attempt to make a particular point but then jumps out of the system of thought when it suits their fancy. Such practice lacks logical consistency and is therefore a logical fallacy. A detractor of the Christian worldview cannot hop into the Christian system of thought by erecting an objection grounded in the Bible and then demand an answer be given without the use of a Bible. Again, they cannot appeal to the Bible in raising their question and then insist we throw our Bible out of the equation when we give an answer!"
The concern raised by this argument is the assertion that there can be a challenge to Biblical views, particularly on ethics, where the skeptic challenges the apologist to appeal to a source other than the Bible. If the skeptic, for example, makes a challenge as to whether it was right for Abraham to go up to the mountain to sacrifice Isaac and the apologist asserts that it was not wrong, because he was commanded to do it by God, then the skeptic's challenge has been sufficiently answered.
However, the apologist is only justified in the case that they have fallen on one side of the Euthyphro dilemma already. If the apologist has asserted that "something is good because God commands it," then they are allowed to use the assertion that God commanded it to establish that it is good. They do not need an external frame of reference. If the apologist asserts, instead, that "God commands it because it is good" then the skeptic is fully justified in asking for an external referent, because the claim that the act in question was good should be the case based on a factor totally independent of God's command. The apologist is obliged to offer that argument in its defense.
Commitments of Divine Command Theory
It is not unreasonable for the skeptic to challenge the commitments of divine command theory by engaging hypothetical situations (whether based on the Bible or otherwise) in order to demonstrate that the system that it creates is not desirable. While this is an intuitionist appeal in ethics, and not one that demonstrates the incoherence of divine command theory, it is generally regarded as a strong appeal. For example:
- Skeptic: Well, if G [God] asserts that you ought to rape your son with a wine bottle, then it follows from (1) that the deontic statement is true. Is it the case that, per (2) raping someone with a wine bottle is intrinsically ethically good?
This differs from the Euthyphro dilemma in that it already assumes that the apologist has asserted that "something is good because God commands it" and then attempts to establish whether or not the command is over some intrinsic property of the action. The basis of this move is to demonstrate that the system of 'divine command theory' is arbitrary, because the ethical values of actions are dependent on the decisions made by a moral agent; God.