  Spinoza defines the term “attribute” thus: “By attribute I understand what the intellect perceives of substance as constituting its essence” (1D4). This definition is reminiscent of Descartes’ notion of attributes as it appears in the Principle of Philosophy insofar as attributes are related to the essence (or essences) of substance. However, as many have noticed, it is not clear from the definition alone what exactly Spinoza means. There are several, by now famous, ambiguities in the  definition.[7]  These, together with the different interpretative options, are discussed in  Section 1.8.