There are but three modes in which surplus wealth can be disposed of. It can be left to the families of the decedents; or it can be bequeathed [leave behind] for public purposes; or, finally, it can be administered during their lives by its possessors (this is what Carnegie proposes). Under its sway we shall have an ideal state, in which the surplus wealth of the few will become, in the best sense the property of the many, because administered for the common good, and this wealth, passing through the hands of the few, can be made a much more potent force for the elevation of our race than if it had been distributed in small sums to the people themselves. Even the poorest can be made to see this, and to agree that great sums gathered by some of their fellow-citizens and spent for public purposes, from which the masses reap the principal benefit, are more valuable to them than if scattered among them through the course of many years in trifling amounts.

What is the main idea of what Carnegie is saying?