 Copernicus was involved not only in natural science and natural philosophy but also—by his postulation of a quantity theory of money and of "Gresham's Law" (in the year, 1519, of Thomas Gresham's birth)—in the philosophy of man.In the early sixteenth century, Plato, who had become a model for philosophy in Italy, especially in Medicean Florence, was represented in Poland in some ways by Adam of Łowicz, author of "Conversations about Immortality".Generally speaking, though, Poland remained Aristotelian.