Logos

As a joint address to Congress doubling as an official statement on foreign policy, Truman's speech needed to convey the president's position as clearly and confidently as possible. Sure, there are some appeals to emotion and other "pathos-invoking" subjects. But the biggest persuasive standouts are his appeals to logic and a sense of reason: his use of logos.

Check out a few prime examples:

The foreign policy and the national security of this country are involved. (2)

This is Truman's way of subtly saying, "Are you guys even listening?" The situation he's discussing involves one of the biggest essentials to our own wellbeing: our safety. You can't just ignore that.

Next up:

The United States must supply that assistance. […] There is no other country to which democratic Greece can turn. No other nation is willing and able to provide the necessary support for a democratic Greek government. (27; 29-30)

"Like seriously," says Truman. Now that the UK is pulling out of Greece, there's no other country that is financially strong enough to help them besides us. This is beyond the scope of what the UN can do. Therefore, by process of elimination—another strategy for appealing to logic—it's up to the U.S. to save the day.

And lastly:

If Greece should fall under the control of an armed minority, the effect upon its neighbor, Turkey, would be immediate and serious. Confusion and disorder might well spread throughout the entire Middle East. (81-82)

Really, isn't the entire domino theory, with its lines of dominoes and sequential reasoning, an appeal to logos?

Truman uses logos for the same reasons we use a mobile app to order pizza: it's simple, straightforward, and easy to get what we want in under twenty minutes. Plus, we all know that pizza and freedom are basically the same thing.