This paper offers a new interpretation of the young Spinoza’s method of distinguishing the true ideas from the false, which shows that his answer to the sceptic is not a failure. This method combines analysis and synthesis as follows: if we can say of the object of an idea which simple things underlie it, how it can be constructed out of simple elements, and what properties it has after it has been produced, doubt concerning the object simply makes no sense. (...) The paper also suggests a way in which this methodology connects to the ontology of the Ethics. (shrink)