DESCARTES TO BERKELEY geometry If the project ultimately fails, it is not the fault of the philosopher but of the nature of philosophy itself As the titles of the diVerent parts show, the treatise deals with many other things besides ethics The Wrst book is a treatise of metaphysics and also a treatise of natural theology: it expounds a theory of the nature of substance which is at the same time an ontological argument for the existence of God Whereas for Descartes there were two fundamental kinds of substance, mental and material, for Spinoza there is only a single substance (which may be called either ‘God’ or ‘Nature’) which possesses both the attribute of thought and the attribute of extension The human mind and the human body, therefore, not belong in two diVerent worlds: the mind, as is explained in the second book, is man considered as a mode of the attribute of thought, and the body is man considered as a mode of the attribute of extension Mind and body are inseparable: the human mind is in fact simply the idea of the human body On this foundation, Spinoza builds up an epistemological theory of three levels of knowledge: imagination, reason, and intuition.11 It is in the third book that we approach the topic of the book’s title Human beings, like all other beings, strive to maintain themselves in existence and to repel whatever threatens their destruction The consciousness of this drive in humans is desire, and when the drive operates freely we feel pleasure, and when it is impeded we feel pain All the complex emotions of humans are derived from these basic passions of desire, pleasure, and pain Our judgements of good and evil, and therefore our actions, are determined by our desires and aversions; but the last two books of the Ethics teach us how to avoid being enslaved by our passions (human bondage) by an intellectual understanding of them (human freedom) The key to this is the distinction between active and passive emotions Passive emotions, like fear and anger, are generated by external forces; active emotions arise from the mind’s own understanding of the human condition Once we have a clear and distinct idea of a passive emotion it becomes an active emotion; and the replacement of passive emotions by active ones is the path of liberation In particular we must give up the passion of fear, and especially the fear of death ‘A free man thinks of 11 Spinoza’s metaphysics is considered in detail in Ch 6, his natural theology in Ch 10, and his epistemology in Ch 67