The book is perhaps the most ambitious attempt to apply the method of Euclid in philosophy. Spinoza puts forward a small number of definitions and axioms from which he attempts to derive hundreds of propositions and corollaries, such as "When the Mind imagines its own lack of power, it is saddened by it", "A free man thinks of nothing less than of death", and "The human Mind cannot be absolutely destroyed with the Body, but something of it remains which is eternal." Spinoza argues through propositions. He holds their conclusion is merely the necessary logical conclusion from combining the provided Definitions and Axioms. He starts with the proposition that "there cannot exist in the universe two or more substances having the same nature or attribute." He follows this by arguing that objects and events must not merely be caused if they occur, but be prevented if they do not. By a logical contradiction, if something is non-contradictory, there is no reason that it should not exist. Spinoza builds from these starting ideas.