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Courage is a concept most frequently defined by example rather than by explanation. That is, when asked the question 'What is courage?' a person is more likely to respond 'Courage is standing up to an angry lion' or 'Courage is Jackie Robinson trotting out to the diamond as the first black man in major league baseball' rather than 'Courage is a personality trait characterised by indifference to danger' or some other such explanation.
Among high school students in the process of preparing their application forms for college, this unusual definatory habit is quite evident, as college admissions departments are disturbingly prone to ask applicants to write single page essays in response to the questions like 'What is courage?' Applicants, instead of taking the obvious, and unfailingly accurate, route and copying the definition of 'courage' from the nearest dictionary, almost invariably write an essay about their dearly departed grandfather who stood up to the neighbourhood bully when he was five years old or some other such laudable achievement. In an extreme example, it is a well-worn legend among college applicants that one student, when faced with exactly this question simply wrote the sentence 'This is courage.' and sent in his application. Of course, the legend ends with the student being admitted to the college and living happily ever after1.
So what is courage? Courage, simply put, is a very, very dangerous trait for someone to have. It is the ability to put aside one's own safety, often ensuring someone else's. This can involve standing in front of someone about to be shot, or marching into battle in front of everyone else. It does not take a rocket scientist to recognise that such activities are extraordinarily dangerous and will severely limit a person's chances of achieving their lifetime ambitions.