The Subjunctive!

This morning, as we were playing with our very cool new 'aqualand' toy, Declan declared "If I were a duck, I could swim in this." The correct use of the subjunctive form of the verb ('were' instead of 'was' for antecedent conditions known to be false - what we in philosophy call 'counterfactuals') means that his grasp of English grammar surpasses most of my undergraduate students!