Legal Definitions - post hoc

Post hoc is a shortened form of the Latin phrase "post hoc, ergo propter hoc," which translates to "after this, therefore because of this." In legal and logical contexts, it refers to a common fallacy where one mistakenly assumes that an event caused another simply because the first event happened before the second. It is the error of confusing a sequence in time with a direct cause-and-effect relationship. Just because two events occur one after the other does not automatically mean the first event was the reason for the second.

• Example 1: Policy and Social Impact

  A city council implements a new initiative to increase public park maintenance. In the following quarter, the city reports a significant decrease in reported instances of minor property crime across various neighborhoods. A council member then publicly declares that the park maintenance initiative is solely responsible for the reduction in crime.

  How it illustrates "post hoc": This scenario demonstrates a post hoc fallacy because while the park maintenance initiative preceded the drop in crime, it doesn't automatically prove causation. Other factors could be at play, such as increased police presence for unrelated reasons, a new community watch program, or a general economic improvement that started around the same time. Attributing the change solely to the park maintenance without further evidence of a direct link would be an instance of post hoc reasoning.

• Example 2: Business and Economic Performance

  A technology company launches a major rebranding campaign, including a new logo, website, and advertising strategy. In the quarter immediately following the campaign's launch, the company reports a substantial increase in its stock price. The CEO then attributes the entire stock price surge solely to the success of the rebranding effort.

  How it illustrates "post hoc": This illustrates post hoc reasoning because, although the stock price increase occurred after the rebranding, other factors might have contributed significantly. For instance, a major competitor might have faced a scandal, the overall market might have experienced an unexpected boom, or the company might have simultaneously announced a breakthrough new product that was already in development. Assuming the rebranding was the *only* cause without deeper analysis is a post hoc error.

• Example 3: Legal Argumentation and Evidence

  During a civil trial concerning a car accident, the plaintiff's attorney argues that because the defendant was observed speeding just moments before the collision, the defendant's speeding must have been the sole cause of the accident.

  How it illustrates "post hoc": This argument relies on a post hoc fallacy. While the defendant's speeding *before* the collision establishes a temporal sequence, it does not, by itself, prove that the speeding was the *sole* cause of the accident. There could be other contributing factors, such as the plaintiff running a red light, a sudden mechanical failure in one of the vehicles, or poor road conditions. Simply being "after this" (the speeding) does not automatically mean "therefore because of this" (the sole cause of the accident), and other evidence would be needed to establish a direct causal link.