Philosophical Thursday

Here's a passage from Rene Descartes' Meditations on First Philosophy from 1641. You may benefit from giving it a few moments of consideration as well:

"For the same reason, although general things may
be imaginary, we are bound to confess that there are
simpler objects which are real and true; such as colors,
quantity or magnitude and number. That is why Physics,
Astronomy, Medicine and those sciences which consider
composite things, are dubious; but Arithmetic, Geometry
and sciences which treat things very simple and general
contain some certainty. For whether I am awake or asleep,
two and three always form five, and a square has four
sides. It does not seem possible that truths so clear
and apparent can be uncertain."