It is true that Descartes initiated a new, individualistic, style of philosophising. Medieval philosophers had seen themselves as principally engaged in transmitting a corpus of knowledge; in the course of transmission they might offer improvements, but these must remain within the bounds set by traditions. Renaissance philosophers had seen themselves as rediscovering and republicizing the lost wisdom of ancient times. It was Descartes who the first philosopher since Antiquity to offer himself as a total innovator; as the person who had the privilege of setting out the truth about man and his universe for the very first time. Where Descartes trod, others followed: Locke, Hume, and Kant each offered their philosophies as new creations, constructed for the first time on sound scientific principles. ‘Read my work, and discard my predecessors’ is a constant them of seventeenth- and eighteenth-century thinkers and writers.
With medieval philosophers like Aquinas, Scotus, and Ockham has to read the texts closely to realise the great degree of innovation that is going on: the new wine is always decanted so carefully into the old bottles. With Descartes and his successors, the difficulty is the opposite: one has to look outside the text to realise that much that is presented as original insight is in fact to be found stated in earlier authors. There is no need to doubt the sincerity of Descartes’ repeated statements that he owed nothing to his scholastic predecessors. He was not a plagiarist, but he had no appreciation of how much he had imbibed from the intellectual atmosphere in which he grew.
Anthony Kenny, A New History of Western Philosophy Vol. 3 – The Rise of Modern Philosophy, p. 40, 2006.