Professor McBride uses a hexagonal “benzene” pattern and Franklin’s X-ray pattern of DNA, to continue his discussion of X-ray crystallography by explaining how a diffraction pattern in “reciprocal space” relates to the distribution of electrons in molecules and to the repetition of molecules in a crystal lattice. He then uses electron difference density mapping to reveal bonds, and unshared electron pairs, and their shape, and to show that they are only one-twentieth as dense as would be expected for Lewis shared pairs.

This lecture asks whether it is possible to confirm the reality of bonds by seeing or feeling them. It first describes the work of “clairvoyant” charlatans from the beginning of the twentieth century, who claimed to “see” details of atomic and molecular structure, in order to discuss proper bases for scientific belief. It then shows that the molecular scale is not inconceivably small, and that Newton and Franklin performed simple experiments that measure such small distances.

Professor McBride begins by following Newton’s admonition to search for the force law that describes chemical bonding. Neither direct (Hooke’s Law) nor inverse (Coulomb, Gravity) dependence on distance will do - a composite like the Morse potential is needed. G. N. Lewis devised a “cubic-octet” theory based on the newly discovered electron, and developed it into a shared pair model to explain bonding.

This lecture examines Inferno IV -VII. Dante’s Limbo, modeled on the classical locus amoenus, is identified as a place of repose and vulnerability. Here, in fact, among the poets of antiquity, the pilgrim falls prey to poetic hubris by joining in their ranks. The pilgrim is faced with the consequences of his poetic vocation when he descends to the circle of lust (Inferno V), where Francesca da Rimini, in her failure to distinguish romance from reality, testifies to the dangers inherent to the act of reading.

This lecture is devoted to the Vita nuova, Dante’s autobiographical account of his “double apprenticeship” in poetry and love. The poet’s love for Beatrice is explored as the catalyst for his search for a new poetic voice. Medieval theories of love and the diverse poetics they inspired are discussed in contrast. The novelty of the poet’s final resolution is tied to the relationship he discovers between love and knowledge.