Abstract

There is a virtual consensus among commentators on Descartes that the causal principle by which he relates the objective reality of his ideas to the formal reality of their causes isindefensible. In particular, Descartes’ claim that this principle follows from the general principle which states that the cause must contain at least as much reality as the effect has been examined and rejected as logically implausible. I challenge this view by showing that there is a logically plausible derivation of the causal principle of ideas from the general causal principle. This result has important implications due to the crucial role the causal principle of ideas plays in Descartes’ first a posteriori argument for the existence of God.