The phrase "a third argument is" is correct and usable in written English.
It can be used when introducing an additional point or reason in a discussion or argument.
Example: "In addition to the first two points, a third argument is that the proposed solution will lead to long-term benefits for the community."
Alternatives: "another point is" or "a further argument is".
A third argument is that higher land taxes would make for more efficient use of land.
A third argument is that Mr. Romney has the momentum in the polls.
A third argument is that Mr. Romney has the momentum in the polls: whether or not he would win an election today, the argument goes, he is on a favorable trajectory that will allow him to win on Tuesday.
A third argument is that inequality perverts politics, with Wall Street's influence in Washington often cited as exhibit A of the unhealthy clout of a plutocratic elite.If these arguments are right, there might be a case for some fairly radical responses, especially a greater focus on redistribution.
As The Times's Nate Silver wrote Friday about arguments touting Romney's chances in the election: "A third argument is that Mr. Romney has the momentum in the polls: whether or not he would win an election today, the argument goes, he is on a favorable trajectory that will allow him to win on Tuesday.
China's overall trade balance was in deficit in the first three months of this year, thanks to strong import growth.A third argument is that China's large surplus on its basic balance (the sum of the current-account and net foreign direct investment) and its huge build-up of foreign reserves are both symptoms of currency undervaluation.
A second argument is for insurance.
A second argument is that staff will benefit.
A second argument is that people with pre-existing conditions would find it hard to get coverage.
A second argument is that parents should have the "choice" to send their child to a school of a particular ethos, however odd.
A second argument is that work at home would cut off employes from needed contacts with their co-workers and others.
