 Arguments by analogy are based on the idea that, if two things are similar, what is true of one of them is likely to be true of the other as well (see entry on  analogy and analogical reasoning).  Analogical arguments are widely used across different domains of human activity, for example in legal contexts (see entry on  precedent and analogy in legal reasoning).  As an example, take an argument for the wrongness of farming non-human animals for food consumption: if an alien species farmed humans for food, that would be wrong; so, by analogy, it is wrong for us humans to farm non-human animals for food. The general idea is captured in the following schema (adapted from the entry on  analogy and analogical reasoning;  S is the source domain and T the target domain of the analogy):