Inaugural Lecture.- Imaginado Creatrix: The Creative versus the Constitutive Function of Man, and the Possible Worlds.- I / The A Prior.- Welcoming Remarks.- Life-world and A Priori in Husserl's Later Thought.- The Transcendental A Priori in Husserl and Kant.- The Affective A Priori.- Special Contribution to the Debate: The Life-World and the A Priori -- Opposites or Complementaries'.- Special Contribution to the Debate: The A Priori of Taste.- Consciousness and Action in Ingarden's Thought.- The A Priori in Ingarden's Theory of Meaning.- Discussion.- II / Activity and Passivity of Consciousness.- The Activity of Consciousness: Husserl and Bergson.- Problems of Continuity in the Perceptual Process.- The A Priori Moment of the Subject-Object Dialectic in Transcendental Phenomenology: The Relation-ship between A Priori and Ideality.- Special Contribution to the Debate: Passivity and Activity of Consciousness in Husserl.- III / Phenomenology and Nature.- Sense-Experience: A Stereoscopic View.- Freedom, Self-Reflection and Inter-subjectivity or Psychoanalysis and the Limits of the Phenomenological Method.- Discussion.- Constitution and Intentionality in Psychosis.- Scientific Information Function and Ingarden's Theory of Forms in the Constitution of the Real World.- Discussion.- Complementary Essays.- Le platonisme de Husserl.- Art, Imagination, and the A Priori.