Free Will and Doubt

As has been previously discussed, Descartes introduces, in the Fourth Meditation, Free Will in order to explain how humans, not God, are responsible for Evil, i. e. via the affirmation of ideas that are not perceived clearly and distinctly.  In contrast, in the Principles of Philosophy, he derives it prior to the establishment of the existence of God, in #VI, as that which "causes us to abstain from giving assent to dubious things".  In other words, in that passage, he conceives the function of Free Will as fundamentally negative, with respect to which a further derivation of a positive function, e. g. affirmation, assent, is thus required.  However, such a proof is lacking, both in the Fourth Meditation, and, later, in the Principles.  Nor does the attribution of the affirmation of 'I think' suffice in that regard--for that idea is clearly and distinctly perceived, whereas what is needed is an account of how ideas not so perceived can be freely assented to, i. e. how humans can be responsible for Evil.  Thus, Principle VI reinforces the suspicion that Descartes' eventual concept of Free Will is no more than an ad hoc device in the service of Theological dogma.