How does Descartes attempt to defeat the sceptic? Does he succeed?
Introduction
When it comes to the possibility of knowledge and true beliefs, Pyrrhonian sceptics either suspend judgement due to insufficient evidence or deny all possibility of knowledge. Descartes uses doubt, similar to the way in which the sceptics doubt, but he uses it in order to find a criterion of truth rather than denying the possibility of truth and knowledge. One could argue that it is his method of doubt that defeats scepticism within the meditations. Descartes use of the method of doubt is almost satirical given that he uses exactly what the Sceptics use in order to defeat scepticism. I shall argue that Descartes doesn’t succeed in defeating the sceptic.
Descriptive View
Descartes’ rule of methodological doubt is to treat every doubtful proposition as if it were false. Within the First Meditation he doubts the reliability of the senses, he suggests one doesn’t know the difference between dreaming and reality and he proposes that there could be a ‘malicious demon’ manipulating us and falsifying our sense of reality. In Descartes’ Discourse on Method and the Meditations he compares the way in which sceptics doubt and remain undecided with the way in which he doubts in order to find a solution; ‘I imitated the sceptics who doubt only for doubting sake, and affect to be always undecided; for, on the contrary, my whole plan had for its aim assurance and the rejection of shifting ground and sand in order to find rock and clay” .He uses the method of doubt in order to find a clear and distinct truth to act as an epistemological foundation or Archimedean point for human knowledge and natural philosophy. At the end of the First Meditation he starts to question his existence, however, one cannot be deceived without existing, and one cannot doubt without the ability to think, and one cannot think without a mind, and the existence of a mind is proof of his existence. This is a self-evident truth and provides Descartes with his epistemological foundation. This is the Cogito; Descartes concludes he exists as a mind at the time he is thinking. Descartes uses this enthymeme as an epistemic Archimedean point, and from this he derives a Criterion of Truth, which is that a perception must be clear and distinct for it to be epistemically true. "I now seem to be able to lay it down as a general rule that whatever I perceive very clearly and distinctly is true." One may read this as Descartes first defeat of Pyrrhonian scepticism, given that he has established with complete certainty that he has knowledge of one thing, his own existence.
Descartes references a ‘perfect God’ later in the Meditations and uses two arguments to prove the existence of God; The Causal Argument and The Ontological Argument. The Causal Argument is based upon Descartes idea of a perfect God, a sentiment which Descartes believes to be an indubitable fact. Descartes calls upon three principles within this argument; the principle of causation, the principle of non-inferiority of the cause and the principle that the cause of an idea can be one of only three possibilities: sensory, artificial or innate. He argues that no human has sensory experience of God, and humans are too imperfect to invent the idea of a perfect God, because of the principle of the non-inferiority of the cause. Therefore, the idea of God is innate, “And indeed it is no surprise that God, in creating me, should have placed this idea in me to be, as it were, the mark of the craftsman stamped on his work” . The cause of the idea of God is His existence, and the effect is our knowledge/idea of God therefore, God exists. The Ontological Argument argues that non-existence is an imperfection, and given that God is perfect, then by definition, God exists. Descartes proved the existence of the external world by using his proof of the existence of a perfect God and his criterion of truth. as a foundation for this. He argues God is not a deceiver and therefore the external world exists. This could be referred to as his final defeat of scepticism.
Critical Discussion
The Cartesian Circle is a criticism of Descartes’ arguments which is based upon a potential mistake in reasoning in Descartes’ arguments within the meditations. Descartes’ proof of the reliability of Clear and Distinct ideas takes as a premise God’s existence as a non-deceiver. However, Descartes’ proofs of God’s existence presuppose the reliability of Clear and Distinct perceptions. Mersenne said in the Second set of objections to the Meditations "you are not yet certain of the existence of God, and you say that you are not certain of anything. It follows from this that you do not yet clearly and distinctly know that you are a thinking thing, since, on your own admission, that knowledge depends on the clear knowledge of an existing God; and this you have not proved in the passage where you draw the conclusion that you clearly know what you are." Without knowledge of God’s existence his knowledge wouldn’t be certain, however, he used his criterion of truth to prove God’s existence. It is for these reasons that some philosophers reject Descartes ideas due to the circular nature of his arguments.
Williams denied that the Cartesian Circle was a ‘vicious’ circle. However, he also said of Descartes’ proofs "The trouble with Descartes's system is not that it is circular; nor that there is an illegitimate relation between the proofs of God and the clear and distinct perceptions…The trouble is that the proofs of God are invalid and do not convince even when they are supposedly being intuited” . Descartes’ arguments for God’s existence have received a lot of criticism, especially the Ontological argument. Within the Ontological argument the relation between a “perfect God” and “existence” is a conceptual truth. Kant said that existence is not a predicate, and because humans can’t experience God one can’t prove his existence. Some philosophers argue that the Ontological argument is valuable only as a supplementary argument to the Causal argument. Gassendi said in the Fifth Set of Objections “existence is not a perfection either in God or in anything else; it is that without which no perfections can be present” . Descartes arguments for the existence of God aren’t necessarily intuitive, and Hobbes said his proofs rely on "a very suspect premise" . Some criticism of Descartes arguments for the existence of God have been based on Descartes’ God being a god of philosophers. The proofs of his existence appeal to philosophers but may be less accessible generally. Russel said of the argument “the argument does not, to a modern mind, seem very convincing” .
Conclusion
Deciding whether Descartes defeated the sceptics is obviously dependent on interpretation. Unlike the other philosophers mentioned, Frankfurt interprets the argument as not trying to prove something entirely true, but instead show
Overall, I believe Descartes proofs are flawed and not particularly convincing; therefore, I wouldn’t necessarily say he succeeded in defeating the Sceptics.