The only ways to attain wealth, according to Oppenheimer

Oppenheimer wrote that there were fundamentally two, and only two, paths to the acquisition of wealth. One route is the production of a good or service and its voluntary exchange for the goods or services produced by others. This method — the method of the free market — Oppenheimer termed "the economic means" to wealth. The other path, which avoids the necessity for production and exchange, is for one or more persons to seize other people's products by the use of physical force. This method of robbing the fruits of another man's production was shrewdly named by Oppenheimer the "political means." Throughout history, men have been tempted to employ the "political means" of seizing wealth rather than expend effort in production and exchange. It should be clear that while the market process multiplies production, the political, exploitative means is parasitic and, as with all parasitic action, discourages and drains off production and output in society.

I happen to agree with Oppenheimer. Do you? What other methods of acquiring wealth are there?