Critical thinking is "the objective analysis and evaluation of an issue in order to form a judgment."
Unfortunately many people don't typically demonstrate the capability of critical thinking.
What is the main obstacle to critical thinking? Mental laziness.
Most recent example is the Rolling Stone's sensational but false story about University of Virginia "Rape on Campus" based on fabricated story from the "victim". Despite many holes in the published story, tens of thousands of people marched to protest UVA administration's handling of the case. The reasons for the protesters to march include: those who read the story accepted the story as "fact" without thinking, many more did not even read the story - their outrage was based on reading the headline in the news or just hearsay!!
Either way, they blindly trusted "authorities", in this case "Rolling Stone", more generally it could be news media/network news, government officials, celebrities, technical experts or even what is stated on Wikipedia. They accept what is stated by "authorities" as facts, truth, without thinking, because the "authorities" thought about it already.
How can one be a critical thinker? Have a reasonable dose of doubt, be analytical - understand what, ask why, know how.
In technical world, even if a conclusion was obtained by a reputable source, a good scientist or engineer will not blindly accept the conclusion as truth, they trust the source but verify the conclusion.
Years ago, when I was in graduate school, my professor came up a clever algorithm to perform a very difficult numerical computation. But its implementation somehow only worked for a special case, but not generally. The professor believed that there were bugs in the his computer program. His first student worked on it for half a year without fixing the problem. He asked me to look into it.
I reviewed his algorithm, re derived all formulas in the algorithm in half day. I found a mistake in his formulas. The program was fixed the next day!!
From half year to half day - that was the difference critical thinking made!
Lack of critical thinking in technical world can lead to wasted time and wasted resource. Lack of critical thinking in societal issues could allow falseness be treated as truth, impact our lives.
Most people have the capability of critical thinking. Please apply your critical thinking capability daily!