The given sentence states that `Either John is stupid or John is lazy`, suggesting that either of the two qualities is true for John but not both. The logic here is If one condition doesn`t hold true, then the other one must be.

Options explained:

I. This statement concludes that if John is lazy, then he is not stupid. This assumption isn`t accurate as the prompt indicates a possibility of either condition being true, but does not define a correlation between the two.

II. This statement suggests that if John is not lazy, then he must be stupid. This deduction aligns with the given prompt because it directly infers from `if not one, then the other`.

III. Identical to II, it carries the same premise and conclusion in the reversed form. If John is not stupid, then he must be lazy, aligning with the prompt`s logic.

IV. This proposition is like option I, presuming a counter-factual relationship which isn`t implied in the prompt.

Therefore, the correct option is 2, i.e. II and III, as these interpretations rightly follow the "Either...Or..." clause inherent in the statement.