Abstract

Spinoza's metaphysical thesis that there is only one substance in the universe but a plurality of modes, each of them falling under an attribute, raises a crucial question. How are modes of thinking, i.e. ideas, related to modes of extension? This paper intends to show that there are at least two answers, depending on an understanding of the equivocal term ‘idea’. If ideas are taken to be mental acts, they are identical with modes of extension. If, however, they are understood in the “objective” way, namely as the conceptual content of mental acts, they correspond to modes of extension. It is argued that this method of disambiguating the term ‘idea’ not only helps to understand Spinoza's famous doctrine of parallelism but that it also provides a solution to two puzzling problems: the possibility of “active affects” and the existence of an eternal mind.