Use & criticism of analogy

• Analogy provides a best explanation style argument when the cause of something cannot be directly observed
• In scientific inference, if we know X is caused by Z, we can infer by analogy that something similar to X is caused by something similar to Z
• Hume argues that the similarity of two effects does not necessarily mean they have similar causes; for example, the smoke produced by fire and dry ice is very similar, but their causes are not similar
• Hume points out the radical disanalogies between the creation of the universe and anything else we know of, questioning the validity of drawing analogies between them
• Hume also argues that we cannot claim there is an analogy between artifacts and natural objects, as artifacts are mechanical with a mathematically precise design, while the universe appears more organic and chaotic
• Paley's argument for design is not necessarily based on an analogy between artifacts and the universe, but on the property of complexity and purpose found in both man-made and natural things