Joint Effect

Definition: One thing is held to cause another when in fact both are the effect of a single underlying cause. This fallacy is often understood as a special case of post hoc ergo prompter hoc. Examples: (i) We are experiencing high unemployment which s being caused by a low consumer demand. (In fact, both may be caused by high interest rates.) (ii) You have a fever and this is causing you to break out in spots. (In fact, both symptoms are caused by the measles.) Proof: Identify the two effects and show that they are caused by the same underlying cause. It is necessary to describe the underlying cause and prove that it causes each symptom.