 Nevertheless, both Descartes and Spinoza provide a starting point for their metaphysical doctrines with their conceptions of God, a starting point that is already infected with idealistic elements if idealism is understood as implying a commitment to the primacy or at least the unavoidability and irreducibility of mental items in the constitution and order of things in general. Both agree that in order to gain insight into the constitution of the world one has to find out what God wants us, or maybe better: allows us to know about it (see, e.g., Descartes: Meditations IV, 7–8 and especially 13; Spinoza: Ethics I, XVI). They also agree that the world is created by God although they have different views as to what this means. Whereas Descartes thinks of God as existing outside the world of the existing things He created (see Meditations III, 13 and 22) Spinoza holds that whatever exists is just a peculiar way in which God is present (see Ethics I, XXV, Corollary). Of all existing things all that God permits us to know clearly and distinctly is (again according to both Descartes and Spinoza) that their nature consists either in thinking or in extension. This claim can be seen as providing in the case of Descartes the basis for his justification of ontological dualism. His distinction between extended and thinking substances is not just meant to give rise to a complete classification of all existing things in virtue of their main attributes but also to highlight the irreducibility of mental (thinking) substances to physical or corporeal (extended) substances because of differences between their intrinsic natures (see, e.g., Meditations VI, 19, and Principles of Philosophy I, 51–54). In the case of Spinoza thinking and extension not only refer to attributes of individual things but primarily to attributes of God (see Ethics II, Proposition I, II, and VII, Scholium), making them the fundamental ways in which God himself expresses his nature in each individual thing. This move gives rise to his ontological monism because he can claim that all individual things are just modes in which God’s presence is expressed according to these attributes.