This paper aims at reconstructing the ethical issues raised by Spinoza's early Treatise on the Emendation of the Intellect. Specifically, I argue that Spinoza takes issue with Descartes’ epistemology in order to support a form of “ethical intellectualism” in which knowledge is envisaged as both necessary and sufficient to reach the supreme good. First, I reconstruct how Descartes exploits the distinction between truth and certainty in his Discourse on the Method. On the one hand, this distinction acts as the basis (...) for Descartes’ epistemological rules while, on the other hand, it implies a “morale par provision” in which adequate knowledge is not strictly necessary to practice virtue. Second, I show that Spinoza rejects the distinction between truth and certainty and thus the methodological doubt. This move leads Spinoza to substitute the Cartesian Cogito with the idea of God as the only adequate standard of knowledge, through which the mind can attain the rules to reach the supreme good. Third, I demonstrate that in the Short Treatise Spinoza develops this view by equating intellect and will and thus maintaining that only adequate knowledge can help to contrast affects. However, I also insist that Spinoza's early epistemology is unable to explain why human beings drop conceive of the idea of God inadequately. Thus, I suggest that in his later writings Spinoza accounts for the insufficiency of adequate knowledge in opposing the power of the imagination and passions by reconnecting the nature of ideas with the mind's conatus. (shrink)