What is the part of speech for the word indispensable?

Freedoms" speech. i have called for personal sacrifice. i am assured of the willingness of almost all americans to respond to that call. a part of the sacrifice means the payment of more money in taxes. in my budget message i shall recommend that a greater portion of this great defense program be paid for from taxation than we are paying today. no person should try, or be allowed, to get rich out of this program; and the principle of tax payments in accordance with ability to pay should be constantly before our eyes to guide our legislation. what argument is roosevelt supporting with his appeal to logic in the underlined section of the excerpt? if americans are willing to trust roosevelt, it only makes sense that he will ensure that the tax money is well managed. if americans are willing to make a personal sacrifice, it only makes sense that they will be seen as both noble and patriotic. if americans feel it is right to enter the war, it only makes sense that they will have to pay more in taxes to cover the costs. if americans feel it is right to pay more taxes, it only makes sense that they should also agree it is right to enter the war.