Abstract

Two fundamentally different conceptions of unity can be found in the philosophical tradition. My thesis is that both of them go back to one text, Plato's Parmenides. Plato argues that if the One is posed as unity (the first hypothesis), the One is unthinkable and unnamable. If the One is posed as being (the second hypothesis), we think a plurality. Plotinus explicitly relates his conception of unity to the Parmenides. The One is the origin of the second hypostasis that is marked by the connection of unity and plurality. The One itself is Apollo, a name that is explained as a polla, that is, the ‘not-many’, is indistinct and beyond being. Characteristic of Neoplatonic thought, for which the term ‘henology’ has been introduced, is the absolute transcendence of the One. According to E. Gilson (Being and Some Philosophers) Neoplatonism is incompatible with ‘the mental universe of Christian thinkers’ on account of its thesis that the One transcends being. Yet two henological moments strongly influenced Christian tradition. The first is the idea of ‘negative theology’. It is perceptible in Nicolaus of Cues, who considers ‘Unity’ the most appropriate name for God. The second moment is the spiritual, mystical idea of ‘the union with the One’ (cf. Master Eckhart). More substantial than Gilson's criticism is the position of Levinas who reproaches classical philosophy with the elimination of plurality. The question is whether unity can be conceived in such a way that the plurality of things is saved. The second conception of unity was developed by Aristotle in his Metaphysics (IV, 2). In a critical reaction to the second hypothesis of the Parmenides he argues that ‘being’ and ‘one’ are identical in reality, but differ conceptually. ‘One’ expresses the undividedness (indivisio) of that which is. What deserves attention is that unity does not deny plurality, but division. Aristotle's exposition became the startingpoint of the 13th century doctrine of the transcendentia. Characteristic of this conception of the one is the transcendentality : the one is a property belonging to every being. The importance of this view is twofold. First, the metaphysical one is clearly distinguished from the mathematical one, that belongs to the category of quantity. Second, from the transcendentality follows that ‘one’ has an analogous character. There is no uniformity in unity. The transcendental one determines being in itself. Is not another type of unity required, that is relational in nature ? Some Dutch philosophers have recently developed a new conception of unity, namely, ‘unity as intersubjectivity’. This conception has a theological root : Thomas Aquinas' interpretation of the doctrine of the Trinity. The modern view of unity as an intersubjective unity of a plurality can be understood as a completion of the transcendental conception of the one. The transcendent conception of the One and the transcendental conception have common traits. Thinking of the one is always a transcending movement. Moreover, it implies the task of a union, for it deals with a unity that is not yet, but must be