Change drives a chariot
But it is hard going.
Plato invoked the gods for inspiration, but conceived of an ideal world beyond the gods of Olympus in which dwelled the source of absolute beauty from which came ideal forms. The physical world was only an imperfect reflection of the ideal world which was perfect and eternal. A human's only goal could be to raise him/herself beyond the physical world by pure reason to see the ineffable absolute beauty. According to Plato, there was only either truth or falsehood; real or unreal.1
A frontier inside, unyielding outside.
Exciting to action; still able,
Yet having (the right hand) severed,
Cut off completely.
In Phaedrus, Plato describes the life of a soul using an analogy of a chariot with two horses and a driver. One horse, representing the baser human desires, would struggle against the other horse and driver who aspired towards loftier things. A man would act basely or nobly depending on the resolve and determination of these opposing factions. In other words, a person's natural will is only to seek God by cultivating his/her virtue, yet s/he also possesses an animal will which only seeks what will gratify his/her senses. A human's will is one and the same with God's, however, whether he accomplishes his goals or not depends on his/her strength of resolve against her/his baser desires. S/he may choose to seek the pleasures of the senses, but s/he will then likely come back in the next life in a lower form, such as an animal. We have only the freedom to choose to succeed or fail since the ultimate goals of humans are the same. When Plato refers to freedom he only means freedom from the bounds of the senses; freedom to see the truth which is the same for everyone.2
Severing the heart,
Obliterating the conscience.
Descartes really only differs from Plato in that he does not use the anthropomorphic analogies, but prefers a more mathematical style to describe very similar ideas. He too works to free himself from his baser desires and aspires to the realm of "pure reason" free from even cultural influences. However, Descartes's goals for an absolute truth and his concept of pure reason had to be culturally inspired. He never claimed that his ideas were divinely inspired, but even divine inspiration would likely be influenced by Christian ideology. This seems to negate his claims to having found such a perfect method.3
Thus the depths are marked out by the chalk-line
And the carpenter's square.
Man's free will, for Descartes, has exactly the same limitations as Plato's "soul" with the greater dilemma of being based on Christian ideals which accepts the idea of an omniscient God.4 If God is omniscient, then all events must be predetermined. And, if all events are predetermined by God, how can man sin? Man still supposedly has free will to do good or evil a la "the fall". Christian mystics explain that a person's will is required for perfecting his/her soul. What the soul actually does is determined by God but sometimes God requires that one soul work harder than another to free him/herself from her/his base desires and even may require that another soul turn away from God in order to teach him/her invaluable lessons that will help him/her better serve God when s/he returns to the "true" path. Free will, then, can be seen as simply a forge of God; sometimes hot and sometimes cold. Yet, it is also useful for the believer to see all events as the result of God's will in order to connect those events and respond to them in the most advantageous way.
1 Plato. Phaedrus; n.d.; rpt. 1987; Cambridge University Press.
3 Descartes, Rene. Discourse on Method; 1637; rpt. 1980; Hacket Publishing Company.