In a letter to Uon Brunschvicg declining an invitation to attend a conference commemorating 250th anniversary of death of Spinoza, Bergson wrote: One could say that all philosophers have two philosophies: their and that of Spinoza.1 It could be said that Bergson's own philosophy is reconception of time following emergence of evolution as a science and discovery of entropy as an irreversible process. As above quotation suggests, however, Bergson's thought on time must be seen as taking place from Spinozism. In this respect, entire oeuvre can be regarded as an effort to rethink as an evolving or, in Bergson's terms, thing. In accordance with this, in The Creative Mind Bergson describes as; substantial, indivisible insofar as it is pure duration but adds that the permanence of substance [is] ... a continuity of change.2 Broadly speaking, Bergsonism can be seen as reconfiguration of Spinozism post Darwin and in light of Boltzmann: that is, as immanence given evolution, entropy, and irreversible time. With introduction of change as only eternal aspect of substance, Spinozian conception of immanent causation, as expression of invariant causes, requires revision. Bergson provides this with concept of virtual tendency. The signifies an immanent, productive mode of causality where change itself is causa sui. This transformation, however, alters both relation between Spinoza's natura naturata (nature according to its products or modes) and natura naturans (nature itself as a thinking thing), and relation between attributes of and Bergson suggests that if time is incorporated into substance effect for him on Spinozism is to accept his philosophy as it is, on side of Extension, but to mutilate it on side of Thought.3 Departing from Spinoza, Bergson draws a qualitative distinction between and thought, defining them as antagonistic tendencies of persistence and change. As thought and are no longer parallel, Bergson distinguishes two equally qualitatively differing forms of common notions: those derived from and those expressed in duration. The aim of what follows be to read Bergson beside Spinoza, not only to reveal indebtedness to Spinoza but, in accordance with intricate nature of Spinoza's ontology, to indicate a far greater complexity and coherence to Bergson's thought than has been observed by most commentators thus far. Problems such as exclusivity of intellect and intuition, conflict between science and philosophy and supposed dichotomy of matter and memory, can all be dispelled when they are seen as attributes of a single enduring substance. Further to this, in reading Bergson next to Spinoza, beginnings of first ontological understanding of implications of Darwin's intuition that nature thinks itself can be discerned. If Spinoza presents problem of immanence of substance to thought, Bergson adds further complication of immanence of change within thought itself. And, as Bergson repeatedly stated, this is great unthought of both philosophy and science. For what limits of scientific and philosophical deduction reveal is that nature does not think like us. The revolution that Bergson insists philosophy must undertake is to relinquish quest to grasp movement of change in thought and to conceive apprehension and expression of change as Essential Freedom The term tendency is first employed in Time and Free Will as a means of critiquing idea of free will without resorting to either determinism or chance. For most part, Bergson's critique replicates Spinoza's. In Ethics Spinoza refutes Cartesian idea of a distinct from, and governing, body. His argument is primarily ontological: where Descartes' held that mind and body are two distinct substances, former determining, or acting on latter, Spinoza conceived of a single substance which expresses its modifications (affectiones) through attributes of extension and thought. …