This dissertation has two main points. First, Aristotle’s logic enables sound conclusions even in the language with empty terms. Second, the paradox of nonexistence is not a threat to Aristotle’s metaphysics. These two points are interconnected. I show that deductive rules in Aristotle’s logic are sound with respect to dictum de omni et de nullo and/or logical square of opposition as a kind of “semantical model”. Truth-conditions of various sentences in Aristotle’s logic, derived from dictum and “modeled by square”, enable sound applications of Aristotle’s syllogistic rules on language with empty terms. The key feature of the proposed truth-conditions is the existential import of affirmative sentences. Proposed truth-conditions, however, are dubious and potentially fallacious from the contemporary point of view. Namely, if every affirmative sentence carries some ontological commitment, then sentences like ‘Chimaera is a fiction of a poet’ or ‘Achilles is non-being’ will ontologically commit us that there are (in Quinean sense) non-existent beings. Naturally, we are not inclined to accept that there exists something that does not exist. Therefore, my first point brings a burden that has to be explained through the second point. The resolution of this puzzle can be summarized as follows. Aristotle would be willing to agree with many contemporary philosophers that existence is not a first-order predicate. The disagreement arises in Aristotle’s insistence that we could not know that something exists unless we know what it is. This statement has two layers. First, for a claim that x exists it is required that we know that x is some determinate being, i.e. an instance of some kind, F or G. Second, the sentence ‘x is F’ should be further explained in the hylomorphic analysis. According to Aristotle, the form of a thing is the cause and principle in virtue of which this thing could be recognized as something, i.e. as an instance of a kind F, and thus, as F thing. The contemporary conception of existential commitment is to some extent applicable in Aristotle’s case. After all, when Aristotle says that x is F, he is saying that being F is predicated. At this point it is crucial to understand that the existence of x is a consequence of predication of being F. Existential commitment, I conclude, follows from predication of being according to the categorical scheme. Sentences like ‘Chimaera is a fiction of a poet’ or ‘Achilles is non-being’ are not affirmative predications with respect to categorical scheme, so contemporary worries about the paradox of non-existence vanish. Precisely such kind of sentences in the medieval period inspired discussion about esse intentionale and entia rationis for which our contemporary worries about extra-mental and extra-linguistic existential commitments are not in question at all. Since ‘being’ is not a first-order predicate – and we may add ‘(not) fictitious’, ‘(not) existent’, ‘(not) imaginary’, etc. – affirmative predications in Aristotle’s logic can carry some existential commitment without the burden of the paradox of non-existence. On top of that, Aristotle’s peculiar profile of metaphysical investigation enables us also to recognize contraries as “ontological furniture of the world”. This fact provides the foundation for logical law of contrary pair of sentences which is unrecognizable in contemporary philosophy. Proposed truth-conditions, thus, ultimately spring out of Aristotle’s metaphysics. Nevertheless, some die-hard Quinean metaphysicist might not be persuaded into the core principles of Aristotelian metaphysics, but this disagreement belongs to second-level discussions. The paradox of non-existence, however, is not Aristotle’s crimen on first-level metaphysics.