Post hoc ergo propter hoc is an informal fallacy that states "Because event Y followed event X, event Y must have been caused by event X". It is a fallacy in which an event is presumed to have been caused by a closely preceding event merely on the grounds of temporal succession. This type of reasoning is fallacious because mere temporal succession does not establish a causal connection. It is often shortened simply to post hoc fallacy. A logical fallacy of the questionable cause variety, it is subtly different from the fallacy cum hoc ergo propter hoc, in which two events occur simultaneously or the chronological ordering is insignificant or unknown. Post hoc ergo propter hoc is a logical fallacy in which one event is interpreted to be the cause of a later event because it occurred earlier.