In the introduction to The Origin of Species, he stated, “I am well aware that scarcely a single point is discussed in this volume on which facts cannot be adduced, often apparently leading to conclusions directly opposite to those at which I arrived.”
Sa introduksyon ng kanyang aklat na "The Origin of the Species", sinabi ni Darwin, "nalalaman ko na walang isa mang argumento na aking inilahad sa aklat na ito ang hindi maaaring gamiting kasangkapan upang makabuo ng konklusyon na direktang kakalaban sa mga katotohanan na aking natuklasan."