Foreword. 1. Prologue: A Remark on the Study of the History of Philosophy. 2. The Background: The Controversy on Psychologism in Philosophy. 3. Husserl and Twardowski: A Philosophical Encounter. 4. The Resurgence of Ontology - Objects of Presentations. 5. The Dispute over Object-Less Presentations. 6. The Epilogue: The End of a History of a Concept? Annex 1: A Note on the Texts. Appendix I: References to Twardowski in Husserl's Published Works. Appendix II: Erdmann's Table of Objects. Appendix III: Twardowski;s Nachlaß. Bibliography.