because it does not take into account other possibilities. To illustrate this more clearly, substitute the letters with premises: If it rains, the street will be wet. The street is wet. Therefore, it rained. Although it is possible that this conclusion is true, it does not necessarily mean it must be true. The street could be wet for a variety of other reasons that this argument does not take into account. If we look at the valid form of the argument, we can see that the conclusion must be true: If it rains, the street will be wet. It rained. Therefore, the street is wet. This argument is valid and, if it did rain, it would also be sound. If statements 1 and 2 are true, it absolutely follows that statement 3 is true. However, it may still be the case that statement 1 or 2 is not true. For example: If Albert Einstein makes a statement about science, it is correct. Albert Einstein states that all quantum mechanics is deterministic. Therefore, it's true that quantum mechanics is deterministic. In this case, statement 1 is false. The particular informal fallacy being committed in this assertion is argument from authority. By contrast, an argument with a formal fallacy could still contain all true premises: If an animal is a dog, then it has four legs. My cat has four legs. Therefore, my cat is a dog. Although 1 and 2 are true statements, 3 does not follow because the argument commits the formal fallacy of affirming the consequent. An argument could contain both an informal fallacy and a formal fallacy yet lead to a conclusion that happens to be true, for example, again affirming the consequent, now also from an untrue premise: If a scientist makes a statement about science, it is correct. It is true that quantum mechanics is deterministic. Therefore, a scientist has made a statement about it. Common examples "Some of your key evidence is missing, incomplete, or even faked! That proves I'm right!" "The vet can't find any reasonable explanation for why my dog died. See! See! That proves that you poisoned him! There’s no other logical explanation!" In the strictest sense, a logical fallacy is the incorrect application of a valid logical principle or an application of a nonexistent principle: Most Rimnars are Jornars. Most Jornars are Dimnars. Therefore, most Rimnars are Dimnars. This is fallacious.