In this chapter, the intellectual life of Jakob von Uexküll is analyzed according to three dimensions: the biographical itinerary and its sociohistorical context; the conceptual formulation and its progression; and the historical-epochal significance of his theory from an archaeological perspective. Within the second dimension, we distinguish four moments of Uexküll’s intellectual history: (1) the period of his academic training, his experimental research in the field of physiology and the introduction of the concept of “building plan” [Bauplan] as object of biology (1892–1905); (2) the early unfolding of his theoretical biology through the notions of conformity to a plan [Planmäßigkeit], perception world [Merkwelt] and Umwelt (1907–1920); (3) the period of theoretical resystematization through the refinement of the concept of Umwelt, the introduction of the notions of “functional circle” [Funktionskreis] and “sequence of impulses” [Impulsfolge], and the outline of a theory of actions (1920–1936); and (4) his last reflections on the problem of solipsism and the relationship between heterogeneous living worlds, through the idea of Nature and the theory of meaning [Bedeutungslehre] (1938–1944).