 In spite of those discrepancies, Mersenne was truly fascinated by the fact that the human mind, in its musical appreciation, is so to speak attuned to mathematical harmonies. The perception of consonance although mediated (and perhaps distorted) by our feeling, is not mere sensual pleasure, as Descartes, for example, seemed to think. Properly understood, it has a rational dimension, as it discloses to men the “universal harmony”, the underlying mathematical order that is present at every level of reality, and that connects them together. Mersenne could have found in Kepler’s Harmonices mundi the idea of such an archetypal harmony, ordering each level of reality, and innate to the human mind. He did not accept however Kepler’s rather dismissive view of music, which had led him to define harmonics in purely geometrical terms, stripped from whatever is sensorial and “acoustic” in it.