While modern theories of knowledge begin with something present to the mind - e.g., Descartes begins with self-evidently true, clear, and simple innate ideas - Vico, begins by asking how it is that the mind comes to have anything present to it at all (Verene, 1981).
And it is precisely to this question that Vico claims to have an answer, indeed, it is the master key of his science. "We find," he says,
"that the principle of these origins both of languages and of letters lies in the fact that the early gentile people, by a demonstrated necessity of nature, were poets who spoke in poetic characters. This discovery, which is the master key of this Science, has cost us the persistent research of almost all our literary life, because with our civilized natures we moderns cannot at all imagine and can understand only by great toil the poetic nature of these first men" (para.34, my emphasis).But to understand what he means here by saying that the early people were, by necessity, poets (where the word "poet" is from the Greek poitetes = one who makes, a maker, an artificer), we must divide the process of making involved into two parts: i) the first, to do with the forming of a sensory topic, and ii) the second, with the forming of an imaginary universal which, from a 'rooting' in it, 'lends' the topic a determinate form.--John Shotter, CMN/UNH, http://pubpages.unh.edu/~jds/VicoNotes.htm