Geologists discover... an almost complete difference to exist between the species or stamp of life, of one epoch from that of every other. We are the… - Patrick Matthew

There is more beauty and unity of design in this continual balancing of life to circumstance, and greater conformity to those dispositions of nature which are manifest to us, than in total destruction and new creation... [The] progeny of the same parents, under great differences of circumstance, might, in several generations, even become distinct species, incapable of co-reproduction.

Throughout this volume, we have felt considerable inconvenience, from the dogmatical classification of plants, and have all along been floundering between species and variety, which certainly under culture soften into each other.

Matthew's response: To me the conception of this law of Nature came intuitively as a self-evident fact, almost without an effort of concentrated thought. Mr Darwin here seems to have more merit in the discovery than I have had; to me it did not appear a discovery. He seems to have worked it out by inductive reason, slowly and with due caution to have made his way synthetically from fact to fact onwards; while with me it was by a general glance at the scheme of Nature that I estimated this select production of species as an a priori recognisable fact – an axiom requiring only to be pointed out to be admitted by unprejudiced minds of sufficient grasp.