Frege's doctrine of the existential quantifier solves the problems of the Ontological Argument. Attempts are often made to apply this notion to existence-statements whose subject is a name. Those whose subjects are empty names, however, are best dealt with by considering senses of names. Sentences which attribute actual existence - e.g. 'X is alive' - cannot be adequately expressed in terms of the quantifier. Thus there is another notion of existence, called esse by Aquinas. Williams's attack on this notion - attempting to show that to use a predicate to express it is paradoxical - and his alternative account, by means of quantifying 're-identifying predicables', both fail. Aquinas, besides a developed theory of esse, shows an appreciation of the Fregean doctrine, distinguishing what is said in answer to the questions quid est? and an est?: the former including esse, the latter being esse ut verum. In this sense the verb 'esse' means 'aliquod dictum est verum': 'X est' depends for support on some true affirmative proposition about X. If 'X' is a nomen naturae (concept-word) it can appear in this supporting proposition as a predicate. Kenny denies this, but the evidence is against him. Attempts to explain away esse, or reduce it to esse ut verum, can be shown to assume it. The distinction between the two notions can be used to dissolve a number of philosophical chimeras. Facts are a confusion between the senses of sentences and per accidens actualities: objects, between names and things. Object theory (ontology) is a confusion between logic and metaphysics, which are distinguished by means of the distinction between the two notions of existence.