What was Carnegie's "gospel of wealth" idea about?

Andrew Carnegie was a famous industrialist who became one of the richest men in America. Hailing originally from a poor background in Scotland, Carnegie immigrated with his family to the United States at the age of thirteen. With his insatiable intellectual curiosity and seemingly inexhaustible capacity for hard work, Carnegie worked his way up from the bottom to achieve untold wealth and success.
In 1901, at the age of 66, Carnegie sold his Pittsburgh steel company to J.P. Morgan for the astonishing sum of $480 million, making him the richest man in America. Long before this, he'd already established a reputation as a generous philanthropist, donating vast sums of his enormous fortune to a variety of charitable causes. This was an example of what Carnegie called, in a famous newspaper article, "The Gospel of Wealth."
What he meant by this is that wealthy people, such as himself, had a social responsibility to use their wealth to help those less fortunate than themselves. The rich should not lead extravagant lifestyles; their surplus wealth would be put to much better use if it were put back into society through philanthropic ventures. Yet Carnegie was at pains to point out that philanthropy should be used to help the poor and underprivileged improve their lives, not to simply give them hand-outs that would do nothing for them in the long-term. To that end, Carnegie founded a number of libraries and educational institutions, which he believed would be the engine of social mobility.