The question before us today is which of these statements is correct: if I was president or if I were president? The problem involves what is called the subjunctive mood of a verb, and as off putting as the terminology might be, we use it (or don’t use it) every day.
Either of these statements, of course, forms part of a larger sentence, perhaps something like If I were president, I would increase our investment in infrastructure. Sentences like this are called conditional: one clause begins with the conjunction if and sets up a condition, and another clause (sometimes introduced by the adverb then, sometimes not) expresses the result that emanates from that condition. The two clauses (condition and result) can appear in reverse order (I would increase our investment in infrastructure if I were president) to stylize the sentence differently, and sometimes the conjunction if does not appear at all (Were I president, I would increase our investment in infrastructure).
Now the question we’re trying to answer—should the verb be were or was—has everything to do with this idea of the result emanating from the condition that has been laid down. Some results follow logically from their condition (if it is raining, there are clouds in the sky), and some are impossible because the condition on which they depend is not true. When the condition is impossible or downright not true, the conditional sentences are called contrary to fact, and that, quite obviously, is what we have in our example. The subject of the sentence is speaking hypothetically, not factually, and that is what will help us determine which verb, was or were, is correct.
Verbs in English can appear in one of three moods (the term derives from the Latin modus meaning way or manner) which tell the reader the way in which the statement is regarded by the writer: as fact (the indicative mood), as command (the imperative mood), or as something hypothetical or speculative (the subjunctive mood). Sometimes we will know the mood by how the verb is spelled, and at other times we will see an auxiliary verb, would or could or might. For our present purposes, we should know that was and were are both forms of the verb be, was the indicative mood and were the subjunctive mood.
So we have now all the information we need to decide between if I was and if I were. We have already determined that the sentence is hypothetical; the subject is clearly not the president and yet is speaking as if he or she holds that position. Something hypothetical, then, requires the subjunctive mood, and the subjunctive form of the verb is were. And so we can confidently and correctly write a contrary-to-fact conditional sentence: If I were president, I would increase our investment in infrastructure. And that’s that.
Conditional sentences and the moods of verbs make up particularly formidable terrain in grammar, not the arid desert often supposed by armchair travelers, but more a boggy marshland of exotic plants and animals where one has to proceed cautiously. One returns from the adventure, though, with a better insight into the subtleties behind the language we use every day—terrain that opens onto critical thinking and clear expression.