Consistency Analogy

A type of Argument by Analogy used to argue for normative consistency: if we treat case A in a certain way (good/bad, permitted/forbidden), we should treat the relevantly similar case B the same way.

1. Cases A and B share morally/legally relevant properties P1, ..., Pn.
2. We judge A to be X (wrong, permitted, required, ...).
∴ 3. We should also judge B to be X.

Example

• “If we ban guns because they kill people, we should ban cars too” (critic responds: cars and guns differ in primary purpose, a relevant disanalogy)
• “If forced organ donation would be wrong, then forcing someone to remain pregnant against their will is also wrong” (Judith Jarvis Thomson’s violinist argument has this structure)
• “We accept that defending oneself with force is justified; analogously, this country was justified in defending itself”

What makes it strong:

• Shared properties are the morally relevant ones, not superficial similarities
• Disanalogies don’t bear on the moral judgement
• The interlocutor accepts the verdict on case A; otherwise the analogy collapses

How it’s attacked:

• Disanalogy: point to a morally relevant difference
• Reject the verdict on A: “actually I don’t think A is wrong either”
• Reductio: accept the analogy and run it to an absurd conclusion to show something has to give

Related

• Argument by Analogy
• Inductive Analogy
• False Analogy
• Ampliative Argument