A common mistake made by those who consider themselves "critical thinkers" is that they assume that they are more or less immune to poor reasoning, as though they are in some way shielded from the effects of bias, prejudice and emotional influences simply by virtue of being a "skeptic" or a "freethinker." Spend enough time on the Internet and you'll see - even amongst the so-called "skeptics" - a proclivity for towing the party line, easy acceptance of ideas and arguments that they prefer, and let's not forget bandwagoning. Members of the skeptical community can be just as susceptible. I've seen it happen. I used to read Pharyngula.
No one is above prejudice. Critical thinking isn't the removal of one's biases, otherwise critical thinking would be impossible. Critical thinking is about recognizing one's biases, and working diligently to keep those biases in check so that one may reason objectively. This requires as much training as any other aspect of intellectual life: sometimes even more. Keep this in mind as we continue on in this series...
- Necessary vs. Sufficient Conditions
Dr. Stark, who was my professor of philosophy and the one who has influenced my thinking more than any other person, once said to me that the key to critical thinking and one of the best indicators that a person has embarked on the path of a critical thinker is that moment when one truly understands the distinction between necessary and sufficient conditions. A necessary condition is a condition which must be satisfied in order to produce X (whatever X might be). A sufficient condition is a condition which guarantees to produce X. Simply put, a necessary condition is needed or required for X, whereas a sufficient condition is enough to produce X. Not all sufficient conditions are necessary, and not all necessary conditions are sufficient. For example, let's say X is fire. The necessary conditions to produce fire are: enough oxygen, enough heat, and enough fuel (i.e., something to burn). Take any one of these three necessary conditions away, and there is no fire. Heat + fuel without oxygen = no fire; fuel + oxygen without heat = no fire, and so on. Each condition is required, thus making them necessary. The three necessary conditions together (oxygen + heat + fuel) make a sufficient condition to produce fire. Getting punched in the face - along with having properly working facial nerves - may certainly be a sufficient condition for my feeling face pain, but it certainly isn't necessary. I could feel face pain from getting kicked in the face, or from walking into a wall. Properly working facial nerves may be a necessary condition for my face to feel pain, but it certainly isn't sufficient, or my face would be in pain all the time (I tried to find a way to work in the "is your face hurting? Because it's killing me!" joke here, but I couldn't... or did I?). For critical thinkers, understanding the distinction between necessary and sufficient conditions isn't merely crucial for its own sake, but it helps us understand the role of reason in the process of critical thinking. Critical thinkers, to borrow Christopher Hitchens' words, "do not rely solely upon science and reason, because these are necessary rather than sufficient factors, but we distrust anything that contradicts science or outrages reason." I have been asked often by theists whether I think reason (or "human reason" as they like to call it) is the "only way" we can know truth. What they're asking is whether I think reason is sufficient. I answer the same way every time: I tell them I don't know, because, well, I really don't know. Theists ask because they want to make room for "revelation" or "faith" as a means of discovering truth, equal to - and in some cases superior to - logic and reason. The problem is that reason often becomes neglected, misused, or discarded entirely. No, I do not say reason is "all you need." All I will say with confidence is that reason is necessary, and to ignore it or attempt to bend it to our will rather than allowing it to lead us to greater understanding is to regress rather than progress.