René Descartes is considered to be the father of modern philosophy. Known arguably for the most famous words in the history of philosophical thought, “I think therefore I am“. He uttered these words in his pursuit of a theory of knowledge that could dispel conclusively the skeptics claim that true knowledge is not possible. As a rationalist he held that only the mind could discover knowledge that is beyond doubt, with a certainty on par with mathematical concepts. He held the senses were not to be trusted to deliver such knowledge. A view contrary to what empiricists such as Locke and Hume held, that only experience, our senses, could give us knowledge of the world. To do this he came up with his method of doubt which was to doubt anything that could be false or was not necessarily true (such as the existence of an actual world outside of his mind). For example he doubted the physical world exists because he could be deceived by an evil demon, or the more modern version which is he could be a brain in a vat that is stimulated by a mad scientists to have the perceptions of a world – either way senses are not reliable according to Descartes. He eventually reached a belief that he thought was impossible to doubt – his own existence as a thinking thing! Hence I think therefore I exist. His existence would then provide the foundation upon which he could build a theory of knowledge that would provide knowledge with certainty.

Now what I found interesting was his thoughts on (1) clear and distinct ideas and how it relates to critical thinking. (2) The reason for error in forming judgement and opinions. In the information facebook and twitter status updating commenting blogging age – where not having an opinion is seen as a deadly sin – Descartes offers some wisdom on critical thinking and why we err.

Clear and distinct ideas essential to critical thinking

“If when I don’t perceive the truth vividly and clearly enough I simply suspend judgment, it’s clear that I am behaving correctly and avoiding error. It is a misuse of my free will to have an opinion in such cases: if I choose the wrong side I shall be in error; and even if I choose the right side, I shall be at fault because I’ll have come to the truth by sheer chance and not through a perception of my intellect”
Descartes believed that each substance had a principle attribute, an essence that made it unique, that made it the kind of thing it is. For example he thought the principle attribute of matter is extension, and the principle attribute of mind is thinking – hence his substance dualism that a human being is a composite of mind and body. To know this principle attribute is to have a clear and distinct idea of what an object is. 
So the first step to critical thinking and forming a judgement is to have a clear and distinct idea of what it is you are thinking of. If I want to form an opinion on a certain concept or issue – do I have a clear and distinct idea of what it is?
In his book, Discourse on Method, he gives 4 principles for critical thinking and arriving at sound judgments.
(1) The first was never to accept anything as true if I didn’t have evident knowledge of its truth: that is, carefully to avoid jumping to conclusions and preserving old opinions, and to include in my judgments only what presented itself to my mind so vividly and so clearly that I had no basis for calling it in question.
(2) The second was to divide each of the difficulties I examined into as many parts as possible and as might be required in order to resolve them better.
(3)The third was to direct my thoughts in an orderly manner, by •starting with the simplest and most easily known objects in order to move up gradually to knowledge of the most complex, and by stipulating some order even among objects that have no natural order of precedence.
(4) And the last was to make all my enumerations so complete, and my reviews so comprehensive, that I could be sure that I hadn’t overlooked anything.

Why we make errors in our thinking – The will over steps it’s limits

“Well, then, where do my mistakes come from? Their source is the fact that my will has a wider scope than my intellect has, so that I am free to form beliefs on topics that I don’t understand. Instead of behaving as I ought to, namely by restricting my will to the territory that my understanding covers, that is, suspending judgment when I am not intellectually in control, I let my will run loose, applying it to matters that I don’t understand. In such cases there is nothing to stop the will from veering this way or that, so it easily turns away from what is true and good. That is the source of my error and sin.“
The reason we often make errors and misinformed opinions and judgments says Descartes is because of our will. Humans have a will and intellect. The will to put in basic terms is where our motives spring from, where our capacity to choose and act originates. The intellect is where our knowledge, beliefs and ideas lie, it is where our reasoning and thinking occurs. Descartes says our will has a wider scope than our intellect. We can form opinions and judgments on topics we have not grasped and understood adequately. We form judgments rather than suspend it on topics we have no clear and distinct ideas of. The will is motivated by more than reason and intellect. Desires, passions and feelings inevitably come into play and we form judgments not based on reasons but on how certain conclusions make us feel.
We are social beings; public opinion and sentiment will often shape our opinion and judgments. I recall when the fees must fall protests began, public opinion was hugely in favour of it. I was swayed not by reasons but more by public opinion which considered free education a common good. My will had already concluded prior to grasping the clear and distinct reasons to support the conclusions (this is not to say there were no sound reasons but only that their soundness was irrelevant compared to the influence of public opinion). And so my will had moved beyond the scope of my intellect. I believed when I should have suspended judgement. So our will, biases and prejudices Descartes says leads to our errors in thinking.
Descartes offers a starting point on how to form good judgments and opinions and be better critical thinkers with his 4 principles. We must have a clear and distinct understanding of the object of our thought. Lastly we should realize the tendency to make judgments on matters we have no understanding of. In the words of Richard Feynman, “The first principle is that you must not fool yourself – and you are the easiest person to fool.”
Further resources:
An excellent talk on cultivating clear thinking from http://www.labri-ideas-library.org called, Thinking Clearly in the Age of Sound-bites and Viral Videos