INTRODUCTION 375
words do not appear in the Meditations). Here was the “clearly and evidently
intuited” knowledge, the starting point, that Descartes had been seeking.
Having established that there is an “I,” a self, a starting point, Descartes began
to explore the nature of this “I”:But what then am I? A thing that thinks. What is that? A thing that doubts, under-
stands, affirms, denies, is willing, is unwilling, and also imagines and has sensory
perceptions.Among the ideas of this “thinking thing” called the “I” is the idea of a per-
fect God. Descartes went on to argue that nothing less than God could have
caused the idea of God. He therefore concluded with a second certainty: that
God exists.
From here Descartes moved to his third certainty: We have a strong tendency to
believe in the existence of a reality beyond our consciousness. If there is no such
external world, then we are terribly deceived. But a perfect God would not allow us
to be unavoidably deceived, since deceit implies imperfection. Accordingly, we
can conclude that we are not misled about those natural beliefs, such as the
existence of an external world, so long as they can withstand the scrutiny of reason
and are not willfully disregarded.The Anatomy Lesson, 1632, by Rembrandt (1606–1669). Members of the Surgeons and Physicians Guild
personify the Age of Observation with their intense scientific inquiry into human anatomy. Descartes was
also interested in anatomy, making such important discoveries as that muscles work in opposition to each
other. (© Heritage Image Partnership Ltd/Alamy Stock)