 Sign-arguments of type (i) and (iii) can always be refuted, even if the premises are true; that is to say that they do not include a valid deduction (sullogismos); Aristotle calls them asullogistos (non-deductive). Sign-arguments of type (ii) can never be refuted if the premise is true, since, for example, it is not possible that someone has fever without being ill, or that someone has milk without having given birth, etc. This latter type of sign-enthymemes is necessary and is also called tekmêrion (proof, evidence). Now, if some sign-enthymemes are valid deductions and some are not, it is tempting to ask whether Aristotle regarded the non-necessary sign-enthymemes as apparent or fallacious arguments. However, there seems to be a more attractive reading: We accept a fallacious argument only if we are deceived about its logical form. But we could regard, for example, the inference “She is pregnant, since she is pale” as a good and informative argument, even if we know that it does not include a logically necessary inference. So it seems as if Aristotle didn’t regard all non-necessary sign-arguments as fallacious or deceptive; but even if this is true, it is difficult for Aristotle to determine the sense in which non-necessary sign-enthymemes are valid arguments, since he is bound to the alternatives of deduction and induction, and neither class seems appropriate for non-necessary sign-arguments.