My friend Nick Gill and I have dedicated more than 20 years to the edition of CD’s Marginalia, CD’s comments to what he was reading while he was reading it. Darwin’s library had been divided by Darwin himself into two large groups, the books and the so-called "pamphlets", that is articles and short books. Moreover we have found handwritten abstracts of books he did not own and his copies of the Gardner ´s Chronicle. We have "visited" CD’s mind and have reconstructed the path he followed pursued throughout his life of studies. We have detected: CD’s reading habits; his responses to what he read; his themes, like leitmotiv around which he would then build complex intellectual structures constituting the foundations of his many theories as detectable in his publications. The "private" Darwin of the Marginalia thus makes sense of the "public" Darwin of The Origin of Species and his other publications.
Keywords: Darwin, Manuscripts, Marginalia, Origin of Species, Theories.