In taking over Descartes' ontological position Kant made an essential omission: he failed to provide an ontology of Dasein. This omission was a decisive one in the spirit [im Sinne] of Descartes' ownmost Tendencies. With the 'cogito sum' Descartes had claimed that he was putting philosophy on a new and firm footing. But what he left undetermined when he began in this 'radical' way, was the kind of Being which belongs to the res cogitans, or—more precisely—the meaning of the Being of the 'sum'.1 By working out the unexpressed ontological foundations of the 'cogito sum', we shall complete our sojourn at the second station along the path of our destructive retrospect of the history of ontology. Our Interpretation will not only prove that Descartes had to neglect the question of Being altogether; it will also show why he came to suppose that the absolute 'Being-certain' ["Gewisssein"] of the cogito exempted him from raising the question of the meaning of the Being which this entity possesses.
Yet Descartes not only continued to neglect this and thus to accept a completely indefinite ontological status for the res cogitans sive mens sive animus ['the thing which cognizes, whether it be a mind or spirit']: he regarded this entity as afundamentum inconcussum, and applied the medieval ontology to it in carrying through the fundamental considerations of his Meditationes. He defined the res cogitans ontologically as an ens; and in the medieval ontology the meaning of Being for such an ens had been fixed by understanding it as an ens creatum. God, as ens infinitum, was the ens increatum. But createdness [Geschaffenheit] in the widest sense of something's having been produced [Hergestelltheit], was an essential [25] item in the structure of the ancient conception of Being. The seemingly new beginning which Descartes proposed for philosophizing has revealed itself as the implantation of a baleful prejudice, which has kept later generations from making any thematic ontological analytic of the 'mind' ["Gemütes"] such as would take the question of Being as a clue and would at the same time come to grips critically with the traditional ancient ontology.
Everyone who is acquainted with the middle ages sees that Descartes is 'dependent' upon medieval scholasticism and employs its terminology. But with this 'discovery' nothing is achieved philosophically as long as it remains obscure to what a profound extent the medieval ontology has influenced the way in which posterity has determined or failed to determine the ontological character of the res cogitans. The full extent of this cannot be estimated until both the meaning and the limitations of the ancient ontology have been exhibited in terms of an orientation directed towards the question of Being.
1 We follow the later editions in reading 'der Seinssinn des "sum" '. The earlier editions have an anacoluthic 'den' for 'der'.