By providing a phenomenological presentation of Aquinas’s duplex operatio intellectus, the author argues that a reader is better equipped to understand where and when Aquinas arrives at the real distinction between essence and existence in the much disputed De Ente et Essentia, chapter four. “Phenomenological presentation” means an honest description of one’s own mental life as it conducts the duplex operatio. From phenomenological observations in the Thomistic texts, the author argues that a penetrative and rebounding movement of attention upon some (...) initially presented multiplicity characterizes the duplex operatio. When this dynamic is conducted upon the multiplicity of a real thing juxtaposed to itself cognitionally existing in sensation, the rebound of the secunda operatio presents the real existence in a sui generis relation of priority to the individual thing understood as existence neutral. Unfortunately, the rebound of attention is too quick to discern accurately the nature of the borderline between the attribute of existence and its subject, the individual thing. The attribute of existence may actuate the thing by shading into it or by remaining distinct from it. Fortunately, the phenomenological situation is sufficient to leave phenomenology and to initiate the third intellectual operation of reasoning. Reasoning concludes to a first cause of phenomenologically observable attributive existence. In this first cause existence is the thing itself. In order for this first cause to have its proper effect corresponding to what it is, the author argues that the second of the above two alternatives for phenomenologically observable attributive existence must be the true one. After linking these reflections to stages of De Ente, chapter 4, the author critically relates them to other interpretations of the text. These interpretations include those of Cahalan, McDonald, Wippel, Dewan, Patt, Kenny, and Owens. (shrink)