It is well known that Husserl considered phenomenology to be First Philosophy—the ultimate science. For Husserl, this means that phenomenology must clarify the ultimate phenomenological-epistemological principle that leads to ultimate elucidation. But what is this ultimate principle and what does ultimate elucidation mean? It is the aim of this paper to answer these questions. In section 2, we shall discuss what role Husserl’s principle of all principles can play in the quest for ultimate elucidation and what it means for a principle to be ultimately elucidating (letztaufklärend) and ultimately elucidated (letztaufgeklärt). We will see that the Husserlian thesis that originary presentive intuitions are an immediate and the ultimate source of justification qualifies as the ultimate epistemological principle.

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 (a) which simple things underlie it, (b) how it can be constructed out of simple elements, and (c) 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.