Herrmann Pidoux and Armand Trousseau stated 'Disease exists within us, because of us, and through us', Pasteur did not entirely disagree, 'This is true for certain diseases', he wrote cautiously, only to add immedately: 'I do not think that it is true for all of them'

Pasteur Vallery-Radot (ed.), Oeuvres de Pasteur (1922–1939), Vol. 6, 167. Quoted in Patrice Debré, Louis Pasteur, trans. Elborg Forster (1994)