PT158 · S3 · Q1 In the previous two years

Circular reasoning occurs when a premise already contains or presupposes the conclusion, such that the argument essentially proves itself by assuming what it set out to demonstrate. That is not what happens here. The premise — that September had more rain than July in the previous two years — is a factual observation about past events. The conclusion — that September will probably have more rain than July this year — is a prediction about the future. These are logically distinct claims: one is about what has already happened, the other about what will happen. The premise does not secretly assume the conclusion; it just provides inadequate evidence for it. The problem is insufficient data, not self-referential logic.

The argument does not discuss average rainfall statistics, nor does it rely on averages that could be distorted by outlier events. The evidence is simply that September had more rain than July in each of the previous two years. The concern about large storms skewing averages is a valid statistical consideration in other contexts, but it does not describe what is happening in this argument. The argument's problem is not that its data might be distorted by outliers; the problem is that there are only two data points in the first place. Even if each year's rainfall figures were perfectly representative and undistorted, two years would still be too few to support a predictive conclusion. This answer addresses a statistical concern that is not relevant to the argument's actual flaw.

This answer describes a flaw in which someone observes that two things often co-occur and concludes they are associated. But the argument here is not about the association between two phenomena — it is about predicting future rainfall based on past rainfall. The argument does not claim that September and heavy rain are "associated" in some general sense; it observes a specific pattern over two years and predicts that pattern will continue. Additionally, this answer mentions "many instances," which mischaracterizes the evidence. The argument relies on only two instances, which is precisely the problem. The flaw described here — correlating co-occurrence with association from many observations — simply does not match the structure of this argument.

The argument does not rely on evidence from a source whose reliability is questionable. It simply states a factual claim about rainfall in the previous two years. There is no cited study, no unnamed expert, no secondhand report — just a direct observation about how much rain fell. The argument's problem has nothing to do with the trustworthiness of its evidence source and everything to do with the quantity of evidence. Even if the two-year rainfall data were obtained from the most reliable meteorological instruments on Earth, two years would still be too few data points to support a weather prediction. This answer raises a concern about evidence reliability that is simply not at issue in the argument.