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<Jean-Baptiste Lamarck> regarded <geology> and the study of living bodies as connected parts of a terrestrial <natural philosophy>. His <Hydrogéologie by Jean-Baptiste Lamarck> and <Zoological Philosophy by Jean-Baptiste Lamarck> sought lawful explanations of the Earth's changing surface and of changing organic organization. The connection was stronger than the commonplace that <organisms> live on land and in water: <fluids> and material transformations were supposed to make both the surface of the globe and living structures intelligible over immense periods.
One important starting point was the replacement of an explanation by exceptional events with a sustained investigation of ordinary causes and their accumulated consequences. Moving water could erode, transport and redeposit material. Over a sufficiently long interval, relatively small actions could change the relation between sea and land. This supplied a way of understanding a surface whose present arrangement need not be its original one. The explanatory appeal was to continuing physical operations plus duration, not to a modern theory of moving lithospheric plates. Calling his programme a fully formed modern <uniformitarianism> would obscure its distinctive mechanisms and assumptions.<Hydrogéologie by Jean-Baptiste Lamarck>[1802, programme of terrestrial physics and the concluding discussion, including printed p. 188 on accumulated fluid action and long duration]{ref}
A related model operated within the <organism>. <Jean-Baptiste Lamarck> distinguished containing <tissues> from contained <fluids>, with moving <fluids> altering the structures through which they passed. More sustained or differently directed activity could strengthen or develop a part, while changing circumstances altered an animal's habits and the employment of its organs. The visible result was to be explained through a material history, rather than through a separate intention directly constructing each useful feature. This is why reducing his whole programme to the slogan that an animal wished for a new organ is misleading. Need, behaviour, <fluid> movement and organization occupied different places in the proposed causal sequence.<Zoological Philosophy by Jean-Baptiste Lamarck>[Part I, chapter VII on circumstances, habits and organs; Part II, chapter I on containing solids and contained fluids]{ref}
There were also chemical connections between living and nonliving nature. In the 1809 work he argued that <organisms> formed their own compound substances and that their remains supplied materials subsequently transformed and simplified outside life. He expressly connected this discussion with <Hydrogéologie by Jean-Baptiste Lamarck>. <Geology> was consequently not a wholly independent history of an inert stage on which <organisms> later appeared. <Organisms> helped produce the materials of that stage; those materials, their environment and their transformations in turn conditioned living activity.<Philosophie zoologique, organic and inorganic productions by Jean-Baptiste Lamarck>[Volume I, printed pp. 91–92: formation of substances by living bodies, their remains and the explicit reference to Hydrogéologie, p. 112]{ref}
The unity of explanation must nevertheless be stated carefully. Sharing physical and chemical causes did not mean that a crystal and an animal were indistinguishable. His comparison of inorganic and living bodies emphasized the organized, heterogeneous, bounded individual, with internal nutrition, development and eventual death. An inorganic aggregate did not acquire those capacities merely by becoming large. The special arrangement and circulation of matter therefore mattered to the explanation of life even when the causes acting on that arrangement were natural. There is no contradiction in claiming lawful material causes while also identifying organizational differences which require explanation.<Philosophie zoologique, living and inorganic bodies by Jean-Baptiste Lamarck>[Part II, chapter I: molecular individuality of inorganic bodies contrasted with organization and contained fluids in living bodies]{ref}
Nor should his <chemistry> be silently translated into modern <biochemistry>. His <fluid> and heat-based explanations, his conjectures about the formation and subsequent simplification of materials, and his accounts of the origin of simple living forms belonged to a particular early nineteenth-century system. To show why they fitted together is not to show that each is now accepted. Modern <observations> that <organisms> alter soils and sediments support some broad connections between life and the Earth's surface, but they do not establish his claim that all compound inorganic materials ultimately derived from living activity.
Finally, the integration helps explain his account of changing <species>. If environments have histories, their inhabitants encounter changing conditions. If habits and organization can respond, and acquired changes can persist through <heredity>, stable-looking forms need not be permanently fixed. His additional tendency toward more complex organization and the modifying effects of circumstances were not identical processes. The natural unity he sought was a framework for explaining both continuity of causes and diversity of outcomes. It was neither Darwinian <natural selection> avant la lettre nor a merely metaphorical comparison between rocks and animals. The conviction followed from a connected programme of material causation, long <time> and the historical production of structure.
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