  If Socrates doesn't exist, “Socrates is wise” (A) and its contrary “Socrates is not-wise” (E) are both automatically false (since nothing—positive or negative—can be truly affirmed of a non-existent subject), while their respective contradictories “Socrates is not wise” (O) and “Socrates is not not-wise” (I) are both true. Similarly, for any object x, either x is red or x is not red—but x may be neither red nor not-red; if, for instance, x is a unicorn or a prime number.