A student and a teacher at Middle School died in car accidents within weeks of each other. Jason Soury, the student, died on Oct. 3, and Maberliz Castillo, the teacher, on Oct. 28. (from NYTimes.com)

BUT

And that was a puzzle to 19th-century disciples of Charles Darwin, such as Herbert Spencer. It was Spencer, an early contributor to The Economist, who invented that poisoned phrase, “survival of the fittest”. (from Economist.com)

Could anyone help with the choice of the articles here. Please? I am sort of aware about the special usage of articles in apposition. Usually it is an 'a'. However, as far as I understood it before stumbling on the latter example, 'the' must be used if the noun is already known to the audience. Hence my confustion as Spencer is mentioned in the first sentence.

Thanks a lot,
Al. 

Nah... does not look that easy

First of all, the people are clearly defined in both examples, not only in the first one. In the former we are talking about Jason Soury and in the latter - Herbert Spencer. So no difference.

About your second remark. True, Spencer is not the only contributor to the magazine, but so is Soury: he is not the only student in the world. No difference here either.

What I am saying is that there must be some difference between those examples, but I cant see it. Are they both appositives?

How2die wrote:

About your second remark. True, Spencer is not the only contributor to the magazine, but so is Soury: he is not the only student in the world. No difference here either.

sam, agreeing that article use is not simple.