This article aims to analyze the empyreal sky theory according
to Cristoporo Borri (1583-1632). That was one of the few theories which,
since the beginning of the 17th century and except for special cases, was
almost exclusively defended by catholic authors and specially jesuits. In
traditional cosmological conception, the empyreal sky was a corporeal
sky that used to limit the universe and in which were placed God and the
well-gifted. There was no physical evidence of that sky and, due to this,
the reasons to defend the existence of the empyreal sky are basically of
theological and philosophical nature. Thus, it is understood that most
of authors who state the existence and discuss the characteristics of that
sky are theologians or philosopher. However, in the first half of 17th
century, a group of jesuit astronomers also struggled in analyzing the
empyreal sky, proposing an integrated view of cosmus where explanations
from theology, philosophy and mathematics matched. Among those
astronomers, the italian Cristoforo Borri, who is the author of Collecta
astronomica ex doctrina, published in Lisbon in 1631 is remarkable. In
this work, which had a great impact in portuguese influenced cultural
world, Borri defended a division of the skies in three parts. According to
that, the universe was organized in aerial sky, ethereal sky and empyreal
sky. What was the nature of this sky? Was the empyreal sky a solid or a
fluid body? What was its shape? These are some of the inquiries analyzed
in this article